bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction in Shapiro Step Height in Double-Barrier Josephson Junction Arrays
Authors: Yamamori Hirotake , Ishizaki Mayumi , Shoji Akira
Published: July 2005

The relationships between the height of the constant voltage step and the difference in the critical current I
c or normal resistance R
n of the upper and lower junctions were numerically calculated. The dependence of the step height on the distribution of the microwave power in a Josephson junction array was also numerically calculated. As a result, it was shown that the difference in R
n significantly reduced the height of the steps, while the uniformity of R
n was actually excellent in our previous experiments. On the other hand, neither the difference in I
c nor the distribution of the microwave power due to attenuation at junctions significantly reduced the step height. The numerical analysis implied that the standing waves in the array due to an impedance mismatch will also significantly reduce the step height.
Field-Effect Transistors Based on Single-Crystalline Wires of Bis-(1, 2, 5-Thiadiazolo)-p-Quinobis(1, 3-Dithiole)
Authors: Fujiwara Eiichi , Takada Masaki , Yamashita Yoshiro , Tada Hirokazu
Published: July 2005

We prepared single-crystalline wires of bis(1, 2, 5-thiadiazolo)-p-quinobis(1, 3-dithiole), whose ends were anchored to the drain and source electrodes of bottom-contact-type field-effect transistors. The temperature dependence of carrier mobility was investigated in the range from 5 K to 330 K. The tunnel transport was found to be dominant at T < 30 K. Thermally activated hopping behavior was observed in the temperature range from 30 K to 200 K. The mobility decreased with increasing temperature at T > 200 K, indicating that phonon scattering governs carrier transport in single-crystalline wires.
Alignment Control of Poly( p-phenylenevinylene) by Atomic Force Microscopy
Authors: Aoki Naofumi , Murayama Akira , Ueda Yasukiyo
Published: July 2005

Alignment control of poly( p-phenylenevinylene) (PPV) induced by rubbing with the cantilever of an atomic force microscope was investigated by polarized fluorescence microscopy. Polymer chains were aligned one-dimensionally by scanning the cantilever in contact with the film surface with a very small load force (1 nN). After rubbing, the PPV film had no grooves and emitted a highly polarized green light. The deformation region of the polymer chain induced by atomic force microscopy rubbing was estimated to be 250 nm wide.
Damping of Solute Convection During Crystal Growth by Applying Magnetic Field Gradients
Authors: Wakayama Nobuko I.
Published: July 2005

One of the advantages of crystal growth under microgravity conditions is the damping of solute convection that affects crystal quality. The mechanism of the dampening effect of magnetic field gradients, B(d
B/d
z), on solute convection was studied, and the magnitude of B(d
B/d
z) required for dampening was calculated. When the absolute value of mass magnetic susceptibility, χg, of a solute is about 70% of that of a solvent (e.g., KCl crystal growth from an aqueous solution) and the weight ratio is 0.26, the gradient to damp convection considerably is estimated to be -3018 T2/m. On the other hand, when the χg of the solute is nearly equal to that of the solvent [protein crystal growth (lysozyme)], a gradient of -1394 T2/m damps convection completely on the earth.
Electron Injection into Si Nanodot Fabricated by Side-Wall Plasma Enhanced Chemical Vapor Deposition
Authors: Ichikawa Kazunori , Punchaipetch Prakaipetch , Yano Hiroshi , Hatayama Tomoaki , Uraoka Yukiharu , Fuyuki Takashi , Takahashi Eiji , Hayashi Tsukasa , Ogata Kiyoshi
Published: July 2005

We have fabricated a floating gate memory using Si nano-crystal dot on thermal SiO2 by a new method of side-wall plasma-enhanced chemical vapor deposition (PECVD) at a low temperature of 430°C. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses revealed that the average dot size and density were approximately 5 nm and 8.5×1011 cm-2, respectively. Electronic properties were investigated with metal–oxide–semiconductor-field-effect transistors (MOSFETs) by embedding the dots into CVD SiO2. Electron charging and discharging effect was clearly confirmed by the transient behavior of the capacitance and the transfer curve at room temperature. The number of electrons confined in a single dot was approximately one.
Large Desorption Yield of Hydrogen Atoms from Silicon Surface in Homogeneous Electron Injection
Authors: Mori Toshiki , Watanabe Satoru
Published: July 2005

The hydrogen desorption yield from a silicon surface in homogeneous electron injection was estimated. To enable homogeneous electron injection into a silicon surface, we used electrons produced in low-pressure argon plasma. The desorption yield we estimated was significantly large compared with that reported previously for electron injection from a sharp tip of a scanning tunneling microscope. The amount of hydrogen desorbed under normal operating conditions for the transistor is close to that for the hole current flowing across an oxide, meaning that desorption could potentially have a large influence on degradation. A positive current-density dependence of the yield was also observed.
Laser Speckle Microscope for Instantaneous Determination of Condition of Single Living Cell
Authors: Hirakawa Yasuyuki , Hasegawa Tomomi , Masujima Tsutomu
Published: July 2005

A laser speckle microscopy imaging system for observation of living cells was developed. This system consists of an optical microscope, a laser source, a single optical fiber, and a video camera. The system has an advantage in that cellular conditions could be instantaneously determined by observing speckle movements. In the experiments, the speckle fluctuations of living and fixed HeLa cells were compared with the change in the temperature of the culture medium around the cells, and their video images were quantitatively analyzed. By applying this system, it is possible to estimate not only cellular activity but also real-time movements of intercellular materials including the cytoplasm without requiring complicated labeling processes.
Fabrication and Field Emission Properties of C60 Nanorod Formed by Spin-Cast Treatment
Authors: Mizukami Hiroyoshi , Ojima Masayoshi , Hiwatashi Shinji , Araki Hisashi , Fujii Akihiko , Ozaki Masanori , Yoshino Katsumi
Published: July 2005

Nanorod-shaped surfaces of C60 films with thicknesses ranging from 100 to 400 nm and lengths ranging from 2 to 3 µm have been successfully obtained by a spin-cast treatment with trans-1,2-dichloroethylene. Results of observations by scanning electron microscopy and field emission (FE) measurements show an obvious correlation between the shape of the C60 nanorods and FE characteristics. By optimizing the conditions of the fabrication processes, the turn-on electric field was lowered from 25–30 to 17–20 V/µm. The nanorod-shaped surfaces of C60 films were still maintained even after a heat treatment under 250°C.
Dynamic Observation of Sweat Glands of Human Finger Tip Using All-Optical-Fiber High-Speed Optical Coherence Tomography
Authors: Ohmi Masato , Nohara Kenji , Ueda Yoshihiro , Fuji Toshie , Haruna Masamitsu
Published: July 2005

High-speed optical coherence tomography (OCT) makes it possible to perform a time-sequential imaging of biological tissue and small organs. In this paper, we demonstrate in vivo observation of dynamics of sweat glands of human finger tip using high-speed OCT with push–pull driven fiber-optic PZT phase modulators. Movement of a sweat droplet through a micro spiral duct can be tracked clearly. An interesting function of sweat glands is found out in time-sequential OCT imaging.
Recovery from Dry Etching Damage in ZnTe by Thermal Annealing
Authors: Guo Qixin , Kume Yusukei , Tanaka Tooru , Nishio Mitsuhiro , Ogawa Hiroshi
Published: July 2005

Thermal annealing has been applied to the recovery from dry-etch-induced damage on ZnTe surfaces. We have demonstrated that the optical property of dry-etched ZnTe can be fully recovered by thermal annealing at temperatures above 300°C for 10 min, indicating that thermal annealing can eliminate the damage on ZnTe induced during reactive ion etching.
Femtosecond Laser Processing of Protein Crystals in Crystallization Drop
Authors: Kashii Masafumi , Kitano Hiroshi , Hosokawa Yoichiroh , Adachi Hiroaki , Mori Yusuke , Sasaki Takatomo , Masuhara Hiroshi , Takano Kazufumi , Matsumura Hiroyoshi , Inoue Tsuyoshi , Murakami Satoshi , Sugamoto Kazuomi , Yoshikawa Hideki
Published: July 2005

We have developed a novel processing technique for protein crystals using femtosecond laser irradiation. We call this technique the femtosecond-laser-induced cut and cleave operation (fs-CACO). By precisely controlling the laser fluence and the position of the laser focal point, we are able to perform accurate and reproducible processing of protein crystals with little damage without troublesome treatment such as the unsealing of vessels and removal of solutions surrounding the crystals. To our knowledge, this is the first report on processing protein crystals using ultra-short-pulse laser ablation. Fs-CACO will be a powerful tool for making problematic protein crystals suitable for X-ray diffraction measurements.
Ion-Beam-Processed SiO2 Film for Homogeneous Liquid Crystal Alignment
Authors: Chou Wei-Yang , Ho Zong-Yeh , Tang Fu-Ching , Mai Yu-Shen , Wu Ting-Yuan , Cheng Horng-Long , Sheu Chia-Rong , Liao Chi-Chang , Liu Kang-Hung
Published: July 2005

Liquid crystals in our experiments could be aligned on a SiO2 surface bombarded by a neutral argon ion beam of an appropriate energy. Also, the pretilt angle of liquid crystals could be varied between 0 and 3.5°, by controlling the argon ion beam with an energy of 500 eV at an incident angle varying from 0 to 85° that was measured from the normal of the substrate. Finally, the twist nematic test cell of the 6 µm cell gap incorporating SiO2 alignment films exhibited a high optical transmission and a fast response time when the angle of the incident ion beam was more than 45°.
Atomic Force Microscope Current-Imaging Study for Current Density through Nanocrystalline Silicon Dots Embedded in SiO2
Authors: Salem Mohamed Ali , Mizuta Hiroshi , Oda Shunri , Fu Ying , Willander Magnus
Published: July 2005

Simultaneous surface and current imaging through nanocrystalline silicon (nc-Si) dots embedded in SiO2 was achieved using a contact mode atomic force microscope (AFM) under a tip-to-sample bias voltages of about 5 V. The obtained images were then analyzed using a one-dimensional model of current density, which took account of the spherical shape of the nc-Si dots, the substrate orientation and the sample bias. A comparison between the experimental and theoretical results showed a fair agreement when the current pass through the dot center, although a large difference was found at a higher voltage. In addition, our model predicted tunneling current oscillations due to a change in tip position relative to the dot center.
Polyvinylidene Flouride Polymer Applied in an Intraocular Pressure Sensor
Authors: Morán Carlos Omar González , Ballesteros Rubén González , Guzmán Maria Dolores Alicia Rodríguez , Gómez Ernesto Suaste
Published: July 2005

An indentation intraocular pressure sensor (IIOPS) was designed and manufactured. It is based on piezoelectric polyvinylidene fluoride (PVDF) films. This sensor will help in the detection and diagnosis of intraocular pressure (IOP) in eye diseases like glaucoma. The pressure in the normal aqueous and vitreous phases is, on average, 15.5 mmHg and up of 21 mmHg when glaucoma exists. The proposed IIOPS offers a measurement range from 10–29 mmHg with a resolution of 1 mmHg and an accuracy of ±0.025.
Effect of Filler Orientation on Thermal Conductivity of Polypropylene Matrix Carbon Nanofiber Composites
Authors: Enomoto Kazuki , Fujiwara Shu , Yasuhara Toshiyuki , Murakami Hiroya , Teraki Junichi , Ohtake Naoto
Published: July 2005

Polypropylene matrix carbon nanofiber composites were obtained by injection molding after kneading with a batch-type twin-screw kneader. The thermal conductivity of the composites in the thickness direction was evaluated, with particular focus on the effects of carbon nanofiber (CNF) content and filler orientation. The thermal conductivity of the composites increased with increasing CNF content, and was obtained as 3.46 W/(m·K) when the CNF content was 50% in weight fraction and the CNFs were highly oriented along the measuring direction of thermal conductivity. This value is approximately seventeenfold higher than that of neat polypropylene.
A Gold-Free Fully Copper-Metallized InP Heterojunction Bipolar Transistor Using Non-Alloyed Ohmic Contact and Platinum Diffusion Barrier
Authors: Chang Shang-Wen , Chang Edward Yi , Lee Cheng-Shih , Chen Ke-Shian , Tseng Chao-Wei , Tu Yong-Ye , Lee Ching-Ting
Published: July 2005

A gold-free, fully Cu-metallized InP heterojunction bipolar transistor using non-alloyed Ti/Pt/Cu and Pt/Ti/Pt/Cu ohmic contacts and platinum diffusion barrier has been successfully fabricated. The InGaAs/Ti/Pt/Cu ohmic structure was stable after annealing up to 350°C as judged from the Auger depth profiles. A current-accelerated stress test was conducted on the device with a current density J
C=80 kA/cm2 for 24 h, and the current gain showed no degradation after the current stress. The devices were also thermally annealed at 200°C for 3 h and showed almost no change in the electrical parameters after the heat treatment. The results show that the Au-free, fully Cu-metallized InP heterojunction bipolar transistor (HBT) can be realized using non-alloyed ohmic contacts and Pt diffusion barrier.
Carrier Mobility in Metal–Oxide–Semiconductor Field Effect Transistor with Atomic-Layer-Deposited Si–Nitride Gate Dielectrics
Authors: Nakajima Anri , Ishii Hiroyuki , Yokoyama Shin
Published: July 2005

n+-poly-Si gate metal–oxide–semiconductor transistors with atomic-layer-deposited (ALD) Si–nitride gate dielectrics were fabricated. Clear saturation characteristics of the drain current were obtained for samples with the Si–nitride gate dielectrics, similar to reference samples with SiO2 gate dielectrics. Slightly smaller electron effective mobility was obtained for the Si nitride dielectrics than that for the SiO2 dielectrics. However, hot-carrier induced mobility degradation and threshold voltage shift in the transistors with the Si–nitride gate dielectrics were found to be less than that in the other transistors. Taking the reduced gate leakage current, suppressed boron penetration, better time-dependent dielectric-breakdown characteristics, and soft breakdown free phenomena for the ALD Si nitride previously reported into account, the ALD Si–nitride gate dielectrics is a promising candidate for sub-100-nm technology generations.
Ga Adlayer Governed Surface Defect Evolution of (0001)GaN Films Grown by Plasma-Assisted Molecular Beam Epitaxy
Authors: Koblmüller Gregor , Brown Jay , Averbeck Robert , Riechert Henning , Pongratz Peter , Speck James S.
Published: July 2005

The impact of the Ga adlayer coverage onto the surface morphologies and pit densities of GaN (0001) films grown by plasma-assisted molecular beam epitaxy (PAMBE) has been studied using quantitative in situ quadrupole mass spectrometry (QMS). As the equilibrium Ga adlayer coverages rise continuously from 0 to 2.5 monolayers (ML) the surface pit densities decrease from ∼2×109 cm-2 to zero, yielding characteristic step-flow and spiral growth hillock features. These results show that there is a direct and quantitative link between Ga adlayer coverage, adatom diffusion and surface defect structure without any discontinuities.
Photoelectrochemical Properties of p-Type GaN in Comparison with n-Type GaN
Authors: Fujii Katsushi , Ohkawa Kazuhiro
Published: July 2005

We studied the photoelectrochemical properties of p-type GaN compared with those of n-type GaN. Band-edge potentials of p-type GaN were determined from the Mott–Schottky plot, and we clarified the potentials to be identical to those of n-type GaN. Photocurrent in p-type GaN shows its potential as an electrode for photoelectrolysis of water.
Collision Models between F- ion and Ar, Kr, and Xe Atoms
Authors: Tong Lizhu , Nanbu Kenichi
Published: July 2005

Collision Models for F-–Ar, F-–Kr, and F-–Xe are obtained using the Monte Carlo technique. The models are determined by comparing the calculated drift velocities of F- ion in Ar, Kr, and Xe gases with the measured data in a wide range of reduced electric field E/N of 2–500 Td (1 Td = 10-21 V m2). The present models are applicable to the particle modeling for the discharges of electronegative gases such as SF6 mixtures.
Sensitivity Characteristics of Positive and Negative Resists at 200 kV Electron-Beam Lithography
Authors: Kim Byung-Sung , Lee Hyo-Sung , Wi Jung-Sub , Jin Kyung-Bae , Kim Ki-Bum
Published: July 2005

The contrast curve of positive and negative electron-beam resists such as polymethylmethacrylate (PMMA), ZEP520A, and hydrogen silsesquioxane (HSQ) at 200 kV electron-beam was estimated by using continuous slow down approximation (CSDA) model with both non-relativistic and relativistic Bethe stopping power. Experimental results show that simple CSDA model well explains the overall response of these various electron-beam resists to high energy electron-beam only if we use the relativistic Bethe stopping power. The difference between non-relativistic and relativistic Bethe stopping power is discussed.
10 Milliwatt Pulse Operation of 265 nm AlGaN Light Emitting Diodes
Authors: Bilenko Yuriy , Lunev Alex , Hu Xuhong , Deng Jianyu , Katona Thomas M , Zhang Jianping , Gaska Remis , Shur Michael S , Sun Wenhong , Adivarahan Vinod , Shatalov Maxim , Khan Asif
Published: July 2005

We report on the development of solid-state deep ultraviolet light sources optimized for the germicidal applications. Pulsed power levels in excess of 10 mW were achieved for AlGaN based 265 nm light emitting diodes by improving the material quality using Migration-Enhanced Metal Organic Chemical Vapor Deposition. Packaged devices reached the continuous-wave power of 237 µW at 30 mA and a pulse power exceeding 10 mW for 1.2 A driving current.
Generation of hypochlorite-modified proteins by neutrophils during ischemia-reperfusion injury in rat liver: attenuation by ischemic preconditioning
Authors: Hasegawa Tadashi , Malle Ernst , Farhood Anwar , Jaeschke Hartmut
Published: July 2005

Although it is well documented that neutrophils are critical for the delayed phase of hepatic ischemia-reperfusion injury, there is no direct evidence for a specific neutrophil-derived oxidant stress in vivo. Therefore, we used a model of 60 min of partial hepatic ischemia and 0–24 h of reperfusion to investigate neutrophil accumulation and to analyze biomarkers for a general oxidant stress [glutathione disulfide (GSSG) and malondialdehyde (MDA)] and for a neutrophil-specific oxidant stress [hypochlorite (HOCl)-modified epitopes] in rats. Plasma alanine transaminase activities and histology showed progressively increasing liver injury during reperfusion, when hepatic GSSG and soluble MDA levels were elevated. At that time, few neutrophils were present in sinusoids. However, the number of hepatocytes positively stained for HOCl-modified epitopes increased from 6 to 24 h of reperfusion, which correlated with the bulk of hepatic neutrophil accumulation and extravasation into the parenchyma. Consistent with a higher oxidant stress at later times, hepatic GSSG and protein-bound MDA levels further increased. Treatment with the NADPH oxidase inhibitor diphenyleneiodonium chloride attenuated postischemic oxidant stress (GSSG, protein-bound MDA, and hepatocytes positively stained for HOCl-modified epitopes) and liver injury at 24 h of reperfusion. Ischemic preconditioning suppressed all oxidant stress biomarkers, liver injury, and extravasation of neutrophils. In conclusion, extravasated neutrophils generate HOCl, which diffuses into hepatocytes and causes oxidative modifications of intracellular proteins during the neutrophil-mediated reperfusion injury phase. Ischemic preconditioning is an effective intervention for reduction of the overall inflammatory response and, in particular, for limitation of the cytotoxic activity of neutrophils during the later reperfusion period.
NH2-terminal signals in ATP7B Cu-ATPase mediate its Cu-dependent anterograde traffic in polarized hepatic cells
Authors: Guo Y. , Nyasae L. , Braiterman L. T. , Hubbard A. L.
Published: July 2005

Cu is an essential cofactor of cellular proteins but is toxic in its free state. The hepatic Cu-ATPase ATP7B has two functions in Cu homeostasis: it loads Cu+onto newly synthesized apoceruloplasmin in the secretory pathway, thereby activating the plasma protein; and it participates in the excretion of excess Cu+into the bile. To carry out these two functions, the membrane protein responds to changes in intracellular Cu levels by cycling between the Golgi and apical region. We used polarized hepatic WIF-B cells and high-resolution confocal microscopy to map the itinerary of endogenous and exogenous ATP7B under different Cu conditions. In Cu-depleted cells, ATP7B resided in a post- trans-Golgi network compartment that also contained syntaxin 6, whereas in Cu-loaded cells, the protein relocated to unique vesicles very near to the apical plasma membrane as well as the membrane itself. To determine the role of ATP7B's cytoplasmic NH2terminus in regulating its intracellular movements, we generated seven mutations/deletions in this large [∼650 amino acid (AA)] domain and analyzed the Cu-dependent behavior of the mutant ATP7B proteins in WIF-B cells. Truncation of the ATP7B NH2terminus up to the fifth copper-binding domain (CBD5) yielded an active ATPase that was insensitive to cellular Cu levels and constitutively trafficked to the opposite (basolateral) plasma membrane domain. Fusion of the NH2-terminal 63 AA of ATP7B to the truncated protein restored both its Cu responsiveness and correct intracellular targeting. These results indicate that important targeting information is contained in this relatively short sequence, which is absent from the related CuATPase, ATP7A.
Nitric oxide inhibits cAMP-dependent CFTR trafficking in intestinal epithelial cells
Authors: Skinn Andrew C. , MacNaughton Wallace K.
Published: July 2005

Nitric oxide is produced during intestinal inflammation and inhibits the epithelial responsiveness to cAMP-dependent secretagogues. The effect is presumably due to inhibition of activation of the CFTR. However, because insertion of CFTR into the epithelial apical membrane is also a cAMP-dependent process, we tested the hypothesis that NO could inhibit cAMP-dependent CFTR trafficking. SCBN intestinal epithelial cells were treated with forskolin to activate adenylate cyclase activity. The cells were fixed at various times and immunostained for CFTR. Some cells were pretreated with the nitric oxide donor PAPA-NONOate, the protein kinase A inhibitor H89, or the microtubule blocker nocodazole. Cross sections of epithelial monolayers were then studied under fluorescence, and the ratio of apical to basolateral CFTR immunoreactivity was determined. Stimulation of adenylate cyclase activity caused an increase in the apical-to-basolateral ratio of CFTR within 30 s. This effect was transient and preceded changes in short-circuit current in SCBN monolayers mounted in Ussing chambers. PAPA-NONOate, H89, and nocodazole all reduced forskolin-stimulated CFTR trafficking. The inhibitory effect of the NO donor was not affected by pretreatment with the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. PAPA-NONOate reduced forskolin-stimulated increases in intracellular cAMP. The data suggest that a portion of the inhibitory effect of nitric oxide donors on cAMP-dependent chloride secretion is through the inhibition of cAMP-dependent insertion of CFTR into the apical plasma membrane. These data provide insight into the mechanism of secretory dysfunction in inflammatory diseases of the gut where mucosal nitric oxide is elevated.
Proteasome degradation of GRK2 during ischemia and ventricular tachyarrhythmias in a canine model of myocardial infarction
Authors: Yu Xichun , Huang Shijun , Patterson Eugene , Garrett Marion W. , Kaufman Kenneth M. , Metcalf Jordan P. , Zhu Meili , Dunn Samuel T. , Kem David C.
Published: July 2005

Arrhythmia-prone subepicardial border zone (EBZ) tissue demonstrates decreased G protein receptor kinase 2 (GRK2) activity and increased sensitivity to isoproterenol 6–24 h after coronary artery ligation (CAL) in the dog. With the use of a semiquantitative immunofluorescence technique, the relative fluorescence intensity (RF) of GRK2 in EBZ decreased to 24% of that in a remote site (RS) ( P < 0.01, n = 30 cells from 3 dogs), whereas GRK5 RF did not change. Confocal studies of cardiac tissue from transgenic mice overexpressing GRK2 validated the use of a semilogarithmic relationship between RF and GRK2 activity. As shown with the use of quantitative real-time RT-PCR, both GRK2 and GRK5 mRNA were not decreased at 24 h in EBZ ( n = 6 dogs) relative to RS control, indicating that the decrease of GRK2 in the EBZ is likely due to posttranscriptional degradation following CAL. Pretreatment of six dogs with the selective proteasome inhibitor bortezomib provided 100% (EBZ) and 50% (infarct) protection against loss of GRK2 at 24 h. There was an absence of rapid (>300 beats/min) and very rapid (>360 beats/min) ventricular triplets that are highly predictive of sudden cardiac death during ECG monitoring in the bortezomib-pretreated animals in contrast to nonpretreated infarcted animals. We have demonstrated that the dramatic decrease in GRK2 in cardiac ischemic tissue can be largely blocked by prior proteasome blockade and that this is associated with significant cardioprotection against malignant ventricular tachyarrhythmias.
Clusterin: a protective mediator for ischemic cardiomyocytes?
Authors: Krijnen P. A. J. , Cillessen S. A. G. M. , Manoe R. , Muller A. , Visser C. A. , Meijer C. J. L. M. , Musters R. J. P. , Hack C. E. , Aarden L. A. , Niessen H. W. M.
Published: July 2005

We examined the relationship between clusterin and activated complement in human heart infarction and evaluated the effect of this protein on ischemic rat neonatal cardiomyoblasts (H9c2) and isolated adult ventricular rat cardiomyocytes as in vitro models of acute myocardial infarction. Clusterin protects cells by inhibiting complement and colocalizes with complement on jeopardized human cardiomyocytes after infarction. The distribution of clusterin and complement factor C3d was evaluated in the infarcted human heart. We also analyzed the protein expression of clusterin in ischemic H9c2 cells. The binding of endogenous and purified human clusterin on H9c2 cells was analyzed by flow cytometry. Furthermore, the effect of clusterin on the viability of ischemically challenged H9c2 cells and isolated adult ventricular rat cardiomyocytes was analyzed. In human myocardial infarcts, clusterin was found on scattered, morphologically viable cardiomyocytes within the infarcted area that were negative for complement. In H9c2 cells, clusterin was rapidly expressed after ischemia. Its expression was reduced after reperfusion. Clusterin bound to single annexin V-positive or annexin V and propidium iodide-positive H9c2 cells. Clusterin inhibited ischemia-induced death in H9c2 cells as well as in isolated adult ventricular rat cardiomyocytes in the absence of complement. We conclude that ischemia induces the upregulation of clusterin in ischemically challenged, but viable, cardiomyocytes. Our data suggest that clusterin protects cardiomyocytes against ischemic cell death via a complement-independent pathway.
Activation of estrogen receptor-α protects the in vivo rabbit heart from ischemia-reperfusion injury
Authors: Booth Erin A. , Obeid Nabeel R. , Lucchesi Benedict R.
Published: July 2005

The estrogen receptor (ER) mediates estrogenic activity in a variety of organs, including those in the reproductive, cardiovascular, immune, and central nervous systems. Experimental studies have demonstrated that 17β-estradiol (E2) protects the heart from ischemia-reperfusion injury. Two estrogen receptors, ERα and ERβ, mediate the actions of estrogen; however, it is not certain which ER mediates the cardioprotective effects of E2. In the present study, the ER-selective agonists 4,4′,4′′-[4-propyl-(1 H)-pyrazole-1,3,5-triyl]tris-phenol (PPT; ERα) and 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; ERβ) were assessed for their cardioprotective potential in an in vivo rabbit model of ischemia-reperfusion injury. Anesthetized female rabbits were administered PPT (3 mg/kg), DPN (3 mg/kg), E2 (20 μg/rabbit), or vehicle intravenously 30 min before a 30-min occlusion of the left anterior descending coronary artery followed by 4 h of reperfusion. Acute treatment with E2 (17.7 ± 2.9%; P < 0.001) and PPT (18.1 ± 2.9%; P < 0.001), but not DPN (45.3 ± 2.4%) significantly decreased infarct size as a percent of area at risk compared with vehicle (45.3 ± 2.4%). Coadministration of PPT or E2 with the ER antagonist ICI-182,780 limited the infarct size-sparing effect of the compounds (43.8 ± 6.6% and 40.6 ± 5.7% respectively, expressed as a percentage of risk region). PPT reduced the release of cardiac-specific troponin-I and reduced the tissue deposition of the membrane attack complex and C-reactive protein similar to that of E2. The results indicate that activation of ERα, but not ERβ, is required for the observed cardioprotective effects of E2.
Activation of PKC modulates blood-brain barrier endothelial cell permeability changes induced by hypoxia and posthypoxic reoxygenation
Authors: Fleegal Melissa A. , Hom Sharon , Borg Lindsay K. , Davis Thomas P.
Published: July 2005

The blood-brain barrier (BBB) is a metabolic and physiological barrier important for maintaining brain homeostasis. The aim of this study was to determine the role of PKC activation in BBB paracellular permeability changes induced by hypoxia and posthypoxic reoxygenation using in vitro and in vivo BBB models. In rat brain microvessel endothelial cells (RMECs) exposed to hypoxia (1% O2-99% N2; 24 h), a significant increase in total PKC activity was observed, and this was reduced by posthypoxic reoxygenation (95% room air-5% CO2) for 2 h. The expression of PKC-βII, PKC-γ, PKC-η, PKC-μ, and PKC-λ also increased following hypoxia (1% O2-99% N2; 24 h), and these protein levels remained elevated following posthypoxic reoxygenation (95% room air-5% CO2; 2 h). Increases in the expression of PKC-ε and PKC-ζ were also observed following posthypoxic reoxygenation (95% room air-5% CO2; 2 h). Moreover, inhibition of PKC with chelerythrine chloride (10 μM) attenuated the hypoxia-induced increases in [14C]sucrose permeability. Similar to what was observed in RMECs, total PKC activity was also stimulated in cerebral microvessels isolated from rats exposed to hypoxia (6% O2-94% N2; 1 h) and posthypoxic reoxygenation (room air; 10 min). In contrast, hypoxia (6% O2-94% N2; 1 h) and posthypoxic reoxygenation (room air; 10 min) significantly increased the expression levels of only PKC-γ and PKC-θ in the in vivo hypoxia model. These data demonstrate that hypoxia-induced BBB paracellular permeability changes occur via a PKC-dependent mechanism, possibly by differentially regulating the protein expression of the 11 PKC isozymes.
Naloxone does not influence cardiovascular responses to mild mental stress in postmenopausal women
Authors: Litschauer Brigitte , Schaller Georg , Wolzt Michael
Published: July 2005

The interaction between central opioid activity, sex hormones, and the cardiovascular reactivity to stress is unknown. Twenty-eight healthy postmenopausal women, 16 without, and 12 with hormone replacement therapy (HRT) participated in this randomized, double-blind, cross-over study. The opioid receptor antagonist naloxone or placebo was administered intravenously on 2 different days and mild mental stress was induced by the Stroop Color-Word Test. Cardiovascular responses were assessed noninvasively by impedance cardiography. Stress significantly increased stroke volume, cardiac output, blood pressure, and heart rate, which was not influenced by opioid receptor blockade. Whereas naloxone increased cortisol plasma concentrations irrespective of HRT status, luteinizing hormone concentrations, which were higher in non-HRT compared with HRT women, were increased by naloxone in women with HRT only. These data suggest that the opioidergic tone of the hypothalamus-pituitary-adrenal axis persists in postmenopausal women, irrespective of HRT use, while the opioidergic tone on the hypothalamus-pituitary-gonadal axis seems to depend on an estrogenic milieu. Naloxone does not alter cardiovascular mental stress reactions in postmenopausal women independent of their hormone substitution status.
Antagonism of corticotropin-releasing hormone alters serotonergic-induced changes in brain temperature, but not sleep, of rats
Authors: Imeri Luca , Bianchi Susanna , Opp Mark R.
Published: July 2005

Serotonin is involved in many physiological processes, including the regulation of sleep and body temperature. Administration into rats of low doses (25, 50 mg/kg) of the 5-HT precursor l-5-hydroxytryptophan (5-HTP) at the beginning of the dark period of the 12:12-h light-dark cycle initially increases wakefulness. Higher doses (75, 100 mg/kg) increase nonrapid eye movement (NREM) sleep. The initial enhancement of wakefulness after low-dose 5-HTP administration may be a direct action of 5-HT in brain or due to 5-HT-induced activation of other arousal-promoting systems. One candidate arousal-promoting system is corticotropin-releasing hormone (CRH) and the hypothalamic-pituitary-adrenal axis. Serotonergic activation by 5-HTP at the beginning of the dark period also induces hypothermia. Because sleep and body temperature are influenced by circadian factors, one aim of this study was to determine responses to 5-HTP when administered at a different circadian time, the beginning of the light period. Results obtained show that all doses of 5-HTP (25–100 mg/kg) administered at light onset initially increase wakefulness; NREM sleep increases only after a long delay, during the subsequent dark period. Serotonergic activation by 5-HTP at light onset induces hypothermia, the time course of which is biphasic after higher doses (75, 100 mg/kg). Intracerebroventricular pretreatment with the CRH receptor antagonist α-helical CRH does not alter the impact of 5-HTP on sleep-wake behavior but potentiates the hypothermic response to 50 mg/kg 5-HTP. These data suggest that serotonergic activation by peripheral administration of 5-HTP may modulate sleep-wake behavior by mechanisms in addition to direct actions in brain and that circadian systems are important determinants of the impact of serotonergic activation on sleep and body temperature.
Sexually dimorphic micturition in rats: relationship of perineal muscle activity to voiding pattern
Authors: Cruz Yolanda , Downie John W.
Published: July 2005

In the present study we examined the possibility that striated muscle activity may underlie sexually dimorphic micturition in rats. Micturition dynamics, the gross anatomy of the external urethral sphincter, and the participation of the striated perineal muscles in micturition were compared in urethane-anesthetized adult male and female rats. Bladder contraction characteristics, particularly the magnitude of bladder high-frequency pressure waves during voiding, differed between sexes. Dissections indicated that the sphincter was more extensive and thicker in males than in females. Electromyography showed that in both sexes the sphincter discharged in bursts that correlated with the rising phase of high-frequency bladder pressure oscillations. Regional differences in discharge pattern were seen in the sphincters of males, with the proximal part of the sphincter showing components activated during bladder filling. Bulbospongiosus, ischiocavernosus, and cremaster muscles also were activated during bladder contraction in males. In both sexes transection of the motor branch of the lumbosacral plexus eliminated the bladder high-frequency oscillations and reduced voided volume. Neurectomy did not affect bladder pressure but reduced voiding efficiency by 45% in males. In females the bladder pressure was dramatically decreased, but voiding efficiency only decreased by 24%. Our findings suggest that, in rats, striated perineal muscles contribute to the sexually dimorphic micturition. Activity of the dimorphic perineal muscles may regulate genital and urinary urethra expulsive functions, helping to expel seminal plug and fluids through the long urethra in the male.
Route-dependent effect of nutritional support on liver glucose uptake
Authors: Chen Sheng-Song , Torres-Sanchez Carlos J , Hosein Nadeen , Zhang Yiqun , Lacy D. Brooks , Chang Chris , McGuinness Owen P.
Published: July 2005

The liver is a major site of glucose disposal during chronic (5 day) total parenteral (TPN) and enteral (TEN) nutrition. Net hepatic glucose uptake (NHGU) is dependent on the route of delivery when only glucose is delivered acutely; however, the hepatic response to chronic TPN and TEN is very similar. We aimed to determine whether the route of nutrient delivery altered the acute (first 8 h) response of the liver and whether chronic enteral delivery of glucose alone could augment the adaptive response to TPN. Chronically catheterized conscious dogs received either TPN or TEN containing glucose, Intralipid, and Travasol for either 8 h or 5 days. Another group received TPN for 5 days, but ∼50% of the glucose in the nutrition was given via the enteral route (TPN+EG). Hepatic metabolism was assessed with tracer and arteriovenous difference techniques. In the presence of similar arterial plasma glucose levels (∼6 mM), NHGU and net hepatic lactate release increased approximately twofold between 8 h and 5 days in TPN and TEN. NHGU (26 ± 1 vs. 23 ± 3 μmol·kg−1·min−1) and net hepatic lactate release (44 ± 1 vs. 34 ± 6 μmol·kg−1·min−1) in TPN+EG were similar to results for TPN, despite lower insulin levels (96 ± 6 vs. 58 ± 16 pM, TPN vs. TPN+EG). TEN does not acutely enhance NHGU or disposition above that seen with TPN. However, partial delivery of enteral glucose is effective in decreasing the insulin requirement during chronic TPN.
Signal-Crosstalk Between Rho/ROCK and c-Jun NH
2
-Terminal Kinase Mediates Migration of Vascular Smooth Muscle Cells Stimulated by Angiotensin II
Authors: Ohtsu Haruhiko , Mifune Mizuo , Frank Gerald D. , Saito Shuichi , Inagami Tadashi , Kim-Mitsuyama Shokei , Takuwa Yoh , Sasaki Terukatsu , Rothstein Jeffrey D. , Suzuki Hiroyuki , Nakashima Hidekatsu , Woolfolk Elethia A. , Motley Evangeline D. , Eguchi Satoru
Published: July 2005

Background—

Rho and its effector Rho-kinase/ROCK mediate cytoskeletal reorganization as well as smooth muscle contraction. Recent studies indicate that Rho and ROCK are critically involved in vascular remodeling. Here, we tested the hypothesis that Rho/ROCK are critically involved in angiotensin II (Ang II)-induced migration of vascular smooth muscle cells (VSMCs) by mediating a specific signal cross-talk.

Methods and Results—

Immunoblotting demonstrated that Ang II stimulated phosphorylation of a ROCK substrate, regulatory myosin phosphatase targeting subunit (MYPT)-1. Phosphorylation of MYPT-1 as well as migration of VSMCs induced by Ang II was inhibited by dominant-negative Rho (dnRho) or ROCK inhibitor, Y27632. Ang II–induced c-Jun NH
2
-terminal kinase (JNK) activation, but extracellular signal-regulated kinase (ERK) activation was not mediated through Rho/ROCK. Thus, infection of adenovirus encoding dnJNK inhibited VSMC migration by Ang II. We have further demonstrated that the Rho/ROCK activation by Ang II requires protein kinase C-δ (PKCδ) and proline-rich tyrosine kinase 2 (PYK2) activation, but not epidermal growth factor receptor transactivation. Also, VSMCs express PDZ-Rho guanine nucleotide exchange factor (GEF) and Ang II stimulated PYK2 association with tyrosine phosphorylated PDZ-RhoGEF.

Conclusions—

PKCδ/PYK2-dependent Rho/ROCK activation through PDZ-RhoGEF mediates Ang II–induced VSMC migration via JNK activation in VSMCs, providing a novel mechanistic role of the Rho/ROCK cascade that is involved in vascular remodeling.
Identification and Characterization of Vascular Calcification–Associated Factor, a Novel Gene Upregulated During Vascular Calcification In Vitro and In Vivo
Authors: Alexander M. Yvonne , Wilkinson Fiona L. , Kirton John Paul , Rock Claire Farrington , Collett Georgina D.M. , Jeziorska Maria , Smyth J. Vincent , Heagerty Anthony M. , Canfield Ann E.
Published: July 2005

Objective—

Vascular calcification, with its increasing clinical sequelae, presents an important and unresolved dilemma in cardiac and vascular practice. We aimed to identify molecules involved in this process to develop strategies for treatment or prevention.

Methods and Results—

Using subtractive hybridization, a novel cDNA, designated vascular calcification–associated factor (VCAF), has been isolated from a bovine retinal pericyte cDNA library generated during the differentiation and mineralization of these cells in vitro. RNA ligase-mediated rapid amplification of cDNA ends was used to compile the 740-bp bovine cDNA sequence. Database searching reveals that VCAF has novel nucleotide/amino acid sequences. RNA analysis confirms that VCAF is upregulated in mineralized pericytes and is present in human calcified arteries but not noncalcified arteries. Protein analysis using a VCAF antibody confirms the presence of an 18-kDa protein in calcified nodules but not in confluent pericytes. Adenoviral antisense VCAF gene delivery reduces VCAF protein levels and accelerates pericyte differentiation compared with controls.

Conclusion—

We demonstrate the isolation of a novel gene, VCAF, which is upregulated during vascular calcification in vitro and in vivo. Antisense VCAF gene delivery accelerates pericyte differentiation, implicating a role for VCAF in this clinically significant pathological process.
Cytoplasmic Expression and Extracellular Deposition of an Antiangiogenic Factor, Pigment Epithelium-Derived Factor, in Human Atherosclerotic Plaques
Authors: Baba Hiromitsu , Yonemitsu Yoshikazu , Nakano Toshiaki , Onimaru Mitsuho , Miyazaki Masanori , Ikeda Yasuhiro , Sumiyoshi Shinji , Ueda Yasuji , Hasegawa Mamoru , Yoshino Ichiro , Maehara Yoshihiko , Sueishi Katsuo
Published: July 2005

Objective—

To assess the expression and distribution of a neurotrophic/antiangiogenic factor, pigment epithelium-derived factor (PEDF), related to angiogenesis that is a possibly key event during atherogenesis in human atherosclerotic plaques.

Methods and Results—

Twenty fresh aortic samples were used for reverse-transcription polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry (IHC). In addition, 80 stocked paraffin blocks of coronary arteries from 40 autopsy cases were also used. IHC revealed divergent staining patterns for PEDF in both the aortas and the coronary arteries tested, ie, “cytoplasmic staining” or “extracellular deposition,” were observed, respectively. In the areas showing cytoplasmic staining, double PEDF was expressed in a majority of the foamy macrophages and in some smooth muscle cells, and the PEDF-positive cell frequency was positively correlated with that of microvessels in a cell-rich area in the coronary arteries (
P
<0.0001). Inversely, extracellular deposition of PEDF was seen in acellular areas and was negatively correlated with the number of microvessels (
P
=0.0003).

Conclusions—

These results suggest that PEDF may function as an antiangiogenic factor when it is deposited onto the extracellular matrix. Thus, PEDF may play a significant role in determining the balance of angiogenesis/ antiangiogenesis during atherogenesis.
Overexpression of Human Apolipoprotein A-II in Transgenic Mice Does Not Impair Macrophage-Specific Reverse Cholesterol Transport In Vivo
Authors: Rotllan Noemí , Ribas Vicent , Calpe-Berdiel Laura , Martín-Campos Jesús M. , Blanco-Vaca Francisco , Escolà-Gil Joan Carles
Published: July 2005

Background—

Overexpression of human apolipoprotein (apo) A-II in transgenic mice induces high-density lipoprotein (HDL) deficiency, and increased atherosclerosis susceptibility only when fed an atherogenic diet. This may, in part, be caused by impairment in reverse cholesterol transport (RCT).

Methods and Results—

[
3
H]cholesterol-labeled macrophages were injected intraperitoneally into mice maintained on a chow diet or an atherogenic diet. Plasma [
3
H]cholesterol did not differ from human apoA-II transgenic and control mice at 24 or 48 hours after the label injection. On the chow diet, human apoA-II transgenic mice presented increased [
3
H]cholesterol in liver (1.3-fold) and feces (6-fold) compared with control mice (
P
<0.05). The magnitude of macrophage-specific RCT did not differ between transgenic and control mice fed the atherogenic diet.

Conclusions—

Human apoA-II maintains effective RCT from macrophages to feces in vivo despite an HDL deficiency. These findings suggest that the increased atherosclerotic lesions observed in apoA-II transgenic mice fed an atherogenic diet are not caused by impairment in macrophage-specific RCT.
Heparin-Binding Epidermal Growth Factor–Like Growth Factor, Collateral Vessel Development, and Angiogenesis in Skeletal Muscle Ischemia
Authors: Chalothorn Dan , Moore Scott M. , Zhang Hua , Sunnarborg Susan W. , Lee David C. , Faber James E.
Published: July 2005

Objective—

Heparin-binding epidermal growth factor–like growth factor (HB-EGF) is a potent mitogen for smooth muscle cells and has been implicated in atherosclerosis, tissue regeneration after ischemia, vascular development, and tumor angiogenesis. We examined the hypothesis that HB-EGF participates in angiogenesis and collateral growth in ischemia.

Methods and Results—

During 3 weeks after femoral artery ligation, no attenuation occurred in recovery of hindlimb perfusion or distal saphenous artery flow in HB-EGF–null (HB-EGF
−/−
) versus wild-type mice. Lumen diameters of remodeled collaterals in gracilis muscle were similar by morphometry (87±8 versus 94±6 μm) and angiography, although medial thickening was reduced. Gastrocnemius muscle underwent comparable angiogenesis (41% and 33% increase in capillary-to-muscle fiber ratio). Renal renin mRNA, arterial pressure, and heart rate during anesthesia or conscious unrestrained conditions were similar between groups. These latter findings validate comparisons of perfusion data and also suggest that differences in arterial pressure and/or renin–angiotensin activity are not masking an otherwise inhibitory effect of HB-EGF absence. Four days after ligation, EGF receptor phosphorylation increased in muscle by 104% in wild-type but by only 30% in HB-EGF
−/−
mice. This argues against compensation by other EGF receptor ligands.

Conclusion—

Our results suggest that HB-EGF is not required for arteriogenesis or angiogenesis in hindlimb ischemia.