bluuebunny/crossref_metadata_2025 huggingface dataset:
High-temperature interaction of nitrogen with thin iron films: Thermal desorption kinetics studies combined with microstructure analysis of Fe–N films
Authors: Lisowski W. , Keim E. G. , Smithers M. A.
Published: May 2003

The interaction of nitrogen with thin iron films at 673 K has been studied by means of thermal desorption mass spectrometry (TDMS) and a combination of scanning electron microscopy and transmission electron microscopy. TDMS spectra indicate the coexistence of atomic and molecular states of nitrogen adsorbed at 673 K and at a nitrogen pressure of 0.75 Pa. The origin of the molecular state is discussed as an intermediate state towards dissociative adsorption of nitrogen. Reconstruction of the polycrystalline iron film occurs as a result of both nitrogen interaction at 673 K and thermal desorption by heating the sample substrate to 950 K. The Fe grains become finer and the Fe film surface shows an increase in roughness upon interaction with nitrogen at 673 K. TDMS heating involves annealing of the Fe film and decomposition of the “surface nitrides.” The bulk structure of the Fe film is affected by the nitrogen-induced reconstruction of its topmost surface region.
Metal–organic interface and charge injection in organic electronic devices
Authors: Scott J. Campbell
Published: May 2003

Charge injection at the interface between metallic electrodes and organic semiconductors plays a crucial role in the performance of organic (opto-)electronic devices. This article discusses the current understanding of the formation of the metal–organic contact and the parameters which control the injection current. Organic semiconductors differ significantly from their inorganic counterparts, primarily because they are amorphous van der Waals solids. As a result the electronic states are highly localized, and charge transport is by site-to-site hopping. Organics can also form clean interfaces with many metals, free of interface states in the gap. Nevertheless, there is generally found to be a significant vacuum level offset, the origins of which are not yet fully understood. Organic semiconductors are frequently free of donor and acceptor dopants, and as a result the depletion depth is larger than the organic layer thickness. Thus the Fermi level in the organic and the charge injection barriers depend most directly on the interface offset. The charge injection process is described as thermally assisted tunneling from the delocalized states of the metal into the localized states of the semiconductor, whose energy includes contributions from the mean barrier height, the image potential, the energetic disorder, and the applied electric field. There is no completely satisfactory analytic theory for the field and temperature dependence of the injection current, which, for well characterized interfaces, exhibits behavior relating to both thermionic emission and field-induced tunneling.
Relation between the ion flux, gas phase composition, and wall conditions in chlorine plasma etching of silicon
Authors: Ullal Saurabh J. , Kim Tae Won , Vahedi Vahid , Aydil Eray S.
Published: May 2003

Transients in plasma composition and positive ion flux due to changing chamber wall conditions during Cl2 plasma etching of Si were studied using multiple plasma and surface diagnostics. In presence of Si and O containing species in the gas phase a glassy silicon oxychloride film coats the chamber walls over a time scale determined by the concentrations of the Si and O containing deposition precursors. This time scale can be a few minutes as in the case of Si etching with Cl2 plasma, where the concentration of silicon chloride etching products can be high, or hours as in the case of a Cl2 plasma maintained in absence of Si wafer, where the Si and O can only come from very slow etching of a quartz window. In either case, SiClx (1⩽x⩽4) and Cl concentrations in the gas phase and the total ion flux impinging on the wafer surface increase as the chamber walls are coated with this glassy film. The increase in SiClx and Cl concentrations are primarily due to lower loss probability of these species by recombination on the chamber walls. The ion flux increases primarily due to higher SiClx concentration in the discharge. During etching of Si, increases in Cl concentration and ion flux through the mechanism described above increases the etching and SiClx production rates. This strong coupling among the discharge properties, the wall conditions, and etching rate lead to transients in plasma operation.
Quick estimation of physical etching of SiO2 among etchers with decoupled plasma sources
Authors: Ding Guowen , Wu Wei-Te , Mak Steve , Yau Wai-Fan
Published: May 2003

A quick estimation method of physical etching was studied among three etchers with decoupled plasma sources and high plasma densities. Experiments performed in three types of decoupled plasma source (DPS) chambers suggest a rough estimation rule: if the same top source and bottom bias powers are applied, SiO2 physical etch rate (ER)×wafer area (A) are comparable for 200 and 300 mm wafers among these DPS chambers. This implies that the recipes from these chambers could be readily scaled up from 200 mm DPS to 300 mm DPS chambers. In addition, experimental results corresponded closely with results predicted by an energy balance model specifically developed for DPS. Beyond a certain threshold, physical etch rates in DPS chambers increase linearly with the bias power. The threshold depends more on source power than on chamber geometry. Both the simple estimation and the model are directly useful for experimental engineers in evaluating physical etching during development of new DPS chambers or in process transfer and optimization.
Inductively coupled plasmas in oxygen: Modeling and experiment
Authors: Kiehlbauch Mark W. , Graves David B.
Published: May 2003

Simulation results and experimental measurements in an oxygen ICP are used to examine transport and reaction in oxygen inductively coupled plasmas. The trends of plasma characteristics with pressure and rf power are considered. We show that the balance between gas phase O2 dissociation and surface O recombination controls the plasma characteristics under the investigated conditions. Neutral density profiles are primarily the result of diffusive transport in balance with fast surface reactions. According to the model, the O(1D), O2(a1Δ), and O2(b1Σ) metastable states play an important role in dissociation, ionization, and attachment kinetics. The O(1S) metastable is not kinetically important.
Effect of pressure on dc planar magnetron sputtering of platinum
Authors: Thomas John H.
Published: May 2003

Argon pressure in the 10 to 200 mTorr range was shown to have a profound effect on the deposition characteristics of nonreactive platinum. Two features were observed. The film thickness does not vary rapidly with deposition pressure, and, the density of the film varies rapidly from near bulk to a much lower value at pressures above 50 mTorr. Films at low pressures have a density of ∼20.8 g/cm3 and well defined “columnar structure.” At high pressures (200 mTorr), the density drops to as low as ∼9 g/cm3. Porosity, or void structure, is dominant at high pressure and the columnar structure is still present.
Effect of cooling conditions on plasma-carbonitrided iron surfaces
Authors: Gontijo Leonardo C. , Machado Rogério , Miola Eduardo J. , Castelleti Luiz C. , Nascente Pedro A. P.
Published: May 2003

Plasma carbonitriding (nitrocarburizing) has been used to improve the tribological and mechanical properties of materials, especially iron-based alloys. In this work, the pulsed glow discharge technique was used for nitrocarburizing pure iron in order to investigate the effect of the cooling conditions on the characteristics of the formed layers. Three sample sets were nitrocarburizing in a gas mixture of 2 vol % CH4, 78 vol % H2, and 20 vol % N2, under a pressure of 400 Pa, discharge frequency of 9 kHz, temperature of 580 °C, during 90 min. One set was cooled under a vacuum, the second set was cooled in air, and the third set was rapidly removed from the furnace at the treatment temperature and quenched in oil. All samples were characterized by optical microscopy, scanning electron microscopy, x-ray diffraction, and Vickers microhardness. Differences in surface composition and morphology were observed, indicating the importance of the cooling rate on the formed layer in these three processes. For all of the samples, three layers were observed: A compound layer, a transformed zone, and a diffusion zone.
Aluminum diffusion and nitrogen sputter yield for nitrogen plasma immersion ion implantation into aluminum
Authors: Manova D. , Attenberger W. , Mändl S. , Stritzker B. , Rauschenbach B.
Published: May 2003

The diffusion process and the absolute sputter yields in the system aluminum–nitrogen are investigated for nitrogen implantation in aluminum at elevated temperatures using plasma immersion ion implantation. The substrates are thin aluminum layers deposited on silicon by vacuum arc deposition. The advantages of these layers are (i) easier preparation for transmission electron microscopy (TEM) investigations and (ii) the exact measurement of the atomic area densities before and after implantation. Nitrogen extending into the material a few hundred nanometers was observed at 485 °C using energy filtered TEM, albeit the diffusing species are Al cations. Holes occurring at the Al/Si interface support this viewpoint. The alternative explanation of Al diffusion into Si can be excluded. In sputter saturation with a N/Al ratio of 1:1 at the surface, a preferential sputtering of nitrogen compared to aluminum with respective sputter yields of 1 and 0.3±0.1 was found using Rutherford backscattering spectrometry.
Compositional and electrical properties of zirconium dioxide thin films chemically deposited on silicon
Authors: Harasek S. , Wanzenboeck H. D. , Bertagnolli E.
Published: May 2003

High-k ZrO2 thin films are grown on p-type silicon by metal–organic chemical vapor deposition based on zirconiumtetrakistrifluoroacetylacetonate as single-source precursor system. Annealing of the as-grown films is performed to investigate the impact of oxidative and reductive atmospheres on thin film properties. The composition of the ultrathin films is examined by Auger spectroscopy, whereas metal–oxide–semiconductor (MOS) structures are employed to extract electrical characteristics. Equivalent oxide thicknesses down to 2 nm and interface trap densities of 5×1011 cm−2 eV−1 at midgap are obtained. MOS capacitors show extremely low leakage currents, promising to reduce gate leakage by more than a factor of 103 compared to SiO2. The correlation between compositional and electrical properties is discussed on the basis of postdeposition annealing procedures resulting in a consistent explanation of the observed effects.
Phase transformation in chromium nitride films
Authors: Chen Hong-Ying , Lu Fu-Hsing
Published: May 2003

The phase transformation of CrN films prepared on (100) Si substrates by cathodic arc plasma deposition was investigated at various temperatures using x-ray diffraction and stress measurements. The films were annealed in a N2/H2=9 reducing atmosphere over the temperature range of 300–1200 °C. X-ray diffraction results showed that an additional Cr2N phase appeared both at temperatures above 1100 °C and over temperatures between 500 and 650 °C. Thermodynamics can explain the formation of Cr2N at temperatures above 1100 °C but not that in the low temperature range. Nevertheless, the residual stresses in the films were determined and found to be relaxed largely over such a low temperature range. The stress states of the films were strongly correlated to the phase transformation of the films. It is concluded that the formation of Cr2N at such low temperatures is mainly due to a nonthermodynamic factor—large stress relaxation occurring in the films. More experimental proof of the stress relaxation-induced phase transformation is presented.
Optical transmittance study of silver particles formed by AgOx thermal decomposition
Authors: Shima Takayuki , Tominaga Junji
Published: May 2003

Silver oxide (AgOx) thin films were found to exhibit localized surface plasmon resonance absorption when they were heated above the decomposition temperature. The resonance absorption for annealed AgO was obvious with the film thickness of 5 nm, and it became weak at 15 nm. Atomic force microscope images of a 15 nm film have shown that various-size particles (diameter in lateral direction: 100–600 nm) are dispersed after annealing at 600 °C. Similar optical and morphological properties were obtained with the oxygen composition ratio in the range of 33–48 at. % (i.e., Ag2O and AgO). AgOx film with about 15 nm thickness is mostly used in super-resolutional near-field structure (super-RENS) when combined with an optical disk for the readout of small marks beyond the diffraction limit. The results did not show, however, any evidence that the absorption properties and the readout process of super-RENS disk are well correlated.
Cleaning of Si and properties of the HfO2–Si interface
Authors: Choi K. , Harris H. , Gangopadhyay S. , Temkin H.
Published: May 2003

The effectiveness of modified Shiraki and RCA cleans on the properties of HfO2 gate dielectric and its interface with silicon has been investigated. Modified Shiraki clean provides atomically flat and more completely hydrogen terminated Si surfaces resulting in sharper low energy electron diffraction images and longer inhibition times for native oxide regrowth. Capacitors based on HfO2 deposited by reactive electron beam evaporation under O2 partial pressure and annealed in H2 atmosphere show different properties, dependent on the cleaning method. Capacitance–voltage curves obtained on RCA cleaned samples show lower capacitance and higher distortion than those of modified Shiraki samples. Analysis of capacitance–voltage curves implies higher density of interfacial traps in RCA cleaned devices and thicker interfacial oxides compared to modified Shiraki clean, resulting in higher effective oxide thickness of the dielectric stack.
Effects of ultraviolet/ozone treatment on benzocyclobutene films
Authors: Viallet Benoı̂t , Daran Emmanuelle , Malaquin Laurent
Published: May 2003

Benzocyclobutene (BCB) is a dielectric polymer resin used in microelectronics for its physical properties and its chemical resistance. UV/ozone photochemical treatment modifies the chemical properties of BCB: It creates a near SiO2 composition oxidized surface layer and degrades the polymer structure of BCB. The oxidized surface layer can be etched with fluoride acid and the degraded layer underneath is soluble with acetone. These BCB chemical modifications may be useful for BCB reworking after polymerization. UV/ozone treatment also has an effect on surface characteristics improving the surface tension and decreasing surface roughness of BCB.
Vacuum deposition of silver island films on chemically modified surfaces
Authors: Malynych Serhiy Z. , Chumanov George
Published: May 2003

The silver island films were vacuum deposited at two different evaporation rates on unmodified indium tin oxide substrates and the substrates modified with molecules containing thiol, pyridyl, and fluorocarbon groups. The films were characterized by UV-visible spectroscopy and scanning electron microscopy. Large variations in the structure and thickness of the island films that were observed between substrates were rationalized in terms of different chemical affinity of the surfaces to the silver metal.
Sensor fault detection in etch based on broadband rf signal observation
Authors: Park H.-M. , Grimard D. S. , Grizzle J. W.
Published: May 2003

To minimize machine downtime in semiconductor plasma etching processes, a sensor fault detection system was developed, employing a broadband rf sensor. The work presented here focuses on detecting errors in the transformer coupled power (TCP) measurement and pressure sensor, though the method has potential for several other sensors. To improve the detection sensitivity, we used real-time machine input estimation, and compared it against actual recipe settings instead of employing the raw rf signals directly. For a main etch process on a Lam TCP 9400SE, ±10% relative deviations in TCP measurement, or ±25% in pressure, can be detected with high accuracy: Detection probability PD≈1 and false alarm rate PF≈0 for both.
Assessing the Impact of the Green Revolution, 1960 to 2000
Authors: Evenson R. E. , Gollin D.
Published: May 2003

We summarize the findings of a recently completed study of the productivity impacts of international crop genetic improvement research in developing countries. Over the period 1960 to 2000, international agricultural research centers, in collaboration with national research programs, contributed to the development of “modern varieties” for many crops. These varieties have contributed to large increases in crop production. Productivity gains, however, have been uneven across crops and regions. Consumers generally benefited from declines in food prices. Farmers benefited only where cost reductions exceeded price reductions.
The Potential for Earthquake Early Warning in Southern California
Authors: Allen Richard M. , Kanamori Hiroo
Published: May 2003

Earthquake mitigation efforts in the United States currently use long-term probabilistic hazard assessments and rapid post-earthquake notification to reduce the potential damage of earthquakes. Here we present the seismological design for and demonstrate the feasibility of a short-term hazard warning system. Using data from past earthquakes, we show that our Earthquake Alarm System (ElarmS) could, with current TriNet instrumentation, issue a warning a few to tens of seconds ahead of damaging ground motion. The system uses the frequency content of the P-wave arrival to determine earthquake magnitude, an approach that allows magnitude determination before any damaging ground motion occurs.
Iron Partitioning in Earth's Mantle: Toward a Deep Lower Mantle Discontinuity
Authors: Badro James , Fiquet Guillaume , Guyot François , Rueff Jean-Pascal , Struzhkin Viktor V. , Vankó György , Monaco Giulio
Published: May 2003

We measured the spin state of iron in ferropericlase (Mg
0.83
Fe
0.17
)O at high pressure and found a high-spin to low-spin transition occurring in the 60- to 70-gigapascal pressure range, corresponding to depths of 2000 kilometers in Earth's lower mantle. This transition implies that the partition coefficient of iron between ferropericlase and magnesium silicate perovskite, the two main constituents of the lower mantle, may increase by several orders of magnitude, depleting the perovskite phase of its iron. The lower mantle may then be composed of two different layers. The upper layer would consist of a phase mixture with about equal partitioning of iron between magnesium silicate perovskite and ferropericlase, whereas the lower layer would consist of almost iron-free perovskite and iron-rich ferropericlase. This stratification is likely to have profound implications for the transport properties of Earth's lowermost mantle.
Decapping and Decay of Messenger RNA Occur in Cytoplasmic Processing Bodies
Authors: Sheth Ujwal , Parker Roy
Published: May 2003

A major pathway of eukaryotic messenger RNA (mRNA) turnover begins with deadenylation, followed by decapping and 5′ to 3′ exonucleolytic decay. We provide evidence that mRNA decapping and 5′ to 3′ degradation occur in discrete cytoplasmic foci in yeast, which we call processing bodies (P bodies). First, proteins that activate or catalyze decapping are concentrated in P bodies. Second, inhibiting mRNA turnover before decapping leads to loss of P bodies; however, inhibiting turnover at, or after, decapping, increases the abundance and size of P bodies. Finally, mRNA degradation intermediates are localized to P bodies. These results define the fluxof mRNAs between polysomes and P bodies as a critical aspect of cytoplasmic mRNA metabolism and a possible site for regulation of mRNA degradation.
Interpenetrating As
20
Fullerene and Ni
12
Icosahedra in the Onion-Skin [As@Ni
12
@As
20
]
3
Ion
Authors: Moses Melanie J. , Fettinger James C. , Eichhorn Bryan W.
Published: May 2003

The [As@Ni
12
@As
20
]
3–
ion was prepared from As
7
3–
and Ni(COD)
2
in ethylenediamine solutions and isolated as the Bu
4
P
+
salt (As, arsenic; Ni, nickel; COD, cyclooctadiene; Bu, butyl; P, phosphorus). The anion contains an icosahedral [Ni
12
(μ
12
-As)]
3–
fragment that resides at the center of an As
20
dodecahedral (fullerene) cage to give an onion-skin–like [As@Ni
12
@As
20
]
3–
cluster with
I

h

point symmetry. The icosahedron and pentagonal dodecahedron are reciprocal platonic solids, and the 32 surface atoms form a dimpled geodesic sphere composed of 60 triangular faces. In the gas phase, the [As@Ni
12
@As
20
]
3–
ion sequentiallyloses all 21 As atoms to form a series of Ni
12
As
21–

x

clusters where 0 ≤
x
≤ 21, inclusively.
Mutations in Dynein Link Motor Neuron Degeneration to Defects in Retrograde Transport
Authors: Hafezparast Majid , Klocke Rainer , Ruhrberg Christiana , Marquardt Andreas , Ahmad-Annuar Azlina , Bowen Samantha , Lalli Giovanna , Witherden Abi S. , Hummerich Holger , Nicholson Sharon , Morgan P. Jeffrey , Oozageer Ravi , Priestley John V. , Averill Sharon , King Von R. , Ball Simon , Peters Jo , Toda Takashi , Yamamoto Ayumu , Hiraoka Yasushi , Augustin Martin , Korthaus Dirk , Wattler Sigrid , Wabnitz Philipp , Dickneite Carmen , Lampel Stefan , Boehme Florian , Peraus Gisela , Popp Andreas , Rudelius Martina , Schlegel Juergen , Fuchs Helmut , de Angelis Martin Hrabe , Schiavo Giampietro , Shima David T. , Russ Andreas P. , Stumm Gabriele , Martin Joanne E. , Fisher Elizabeth M. C.
Published: May 2003

Degenerative disorders of motor neurons include a range of progressive fatal diseases such as amyotrophic lateral sclerosis (ALS), spinal-bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Although the causative genetic alterations are known for some cases, the molecular basis of many SMA and SBMA-like syndromes and most ALS cases is unknown. Here we show that missense point mutations in the cytoplasmic dynein heavy chain result in progressive motor neuron degeneration in heterozygous mice, and in homozygotes this is accompanied by the formation of Lewy-like inclusion bodies, thus resembling key features of human pathology. These mutations exclusively perturb neuron-specific functions of dynein.
Human Chromosome 7: DNA Sequence and Biology
Authors: Scherer Stephen W. , Cheung Joseph , MacDonald Jeffrey R. , Osborne Lucy R. , Nakabayashi Kazuhiko , Herbrick Jo-Anne , Carson Andrew R. , Parker-Katiraee Layla , Skaug Jennifer , Khaja Razi , Zhang Junjun , Hudek Alexander K. , Li Martin , Haddad May , Duggan Gavin E. , Fernandez Bridget A. , Kanematsu Emiko , Gentles Simone , Christopoulos Constantine C. , Choufani Sanaa , Kwasnicka Dorota , Zheng Xiangqun H. , Lai Zhongwu , Nusskern Deborah , Zhang Qing , Gu Zhiping , Lu Fu , Zeesman Susan , Nowaczyk Malgorzata J. , Teshima Ikuko , Chitayat David , Shuman Cheryl , Weksberg Rosanna , Zackai Elaine H. , Grebe Theresa A. , Cox Sarah R. , Kirkpatrick Susan J. , Rahman Nazneen , Friedman Jan M. , Heng Henry H. Q. , Pelicci Pier Giuseppe , Lo-Coco Francesco , Belloni Elena , Shaffer Lisa G. , Pober Barbara , Morton Cynthia C. , Gusella James F. , Bruns Gail A. P. , Korf Bruce R. , Quade Bradley J. , Ligon Azra H. , Ferguson Heather , Higgins Anne W. , Leach Natalia T. , Herrick Steven R. , Lemyre Emmanuelle , Farra Chantal G. , Kim Hyung-Goo , Summers Anne M. , Gripp Karen W. , Roberts Wendy , Szatmari Peter , Winsor Elizabeth J. T. , Grzeschik Karl-Heinz , Teebi Ahmed , Minassian Berge A. , Kere Juha , Armengol Lluis , Pujana Miguel Angel , Estivill Xavier , Wilson Michael D. , Koop Ben F. , Tosi Sabrina , Moore Gudrun E. , Boright Andrew P. , Zlotorynski Eitan , Kerem Batsheva , Kroisel Peter M. , Petek Erwin , Oscier David G. , Mould Sarah J. , DoÌhner Hartmut , DoÌhner Konstanze , Rommens Johanna M. , Vincent John B. , Venter J. Craig , Li Peter W. , Mural Richard J. , Adams Mark D. , Tsui Lap-Chee
Published: May 2003

DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.
ISOLATING CARDINAL INVARIANTS
Authors: ZAPLETAL JINDŘICH
Published: May 2003

There is an optimal way of increasing certain cardinal invariants of the continuum.
Rosuvastatin Decreases Caveolin-1 and Improves Nitric Oxide–Dependent Heart Rate and Blood Pressure Variability in Apolipoprotein E
−/−
Mice In Vivo
Authors: Pelat Michel , Dessy Chantal , Massion Paul , Desager Jean-Pierre , Feron Olivier , Balligand Jean-Luc
Published: May 2003

Background—

Decreased heart rate variability (HRV) and increased blood pressure variability (BPV), determined in part by nitric oxide (NO)–dependent endothelial dysfunction, are correlated with adverse prognosis in cardiovascular diseases. We examined potential alterations in BPV and HRV in genetically dyslipidemic, apolipoprotein (apo) E
−/−
, and control mice and the effect of chronic statin treatment on these parameters in relation to their NO synthase (NOS)–modifying properties.

Methods and Results—

BP and HR were recorded in unrestrained, nonanesthetized mice with implanted telemetry devices with or without rosuvastatin. Cardiac and aortic expression of endothelial NOS and caveolin-1 were measured by immunoblotting. Both systolic BP and HR were elevated in apoE
−/−
mice, with abolition of their circadian cycles. Spectral analysis showed an increase in their systolic BPV in the very-low-frequency (+17%) band and a decrease in HRV in the high-frequency (−57%) band, reflecting neurohumoral and autonomic dysfunction. Decreased sensitivity to acute injection of atropine or an NOS inhibitor indicated basal alterations in both parasympathetic and NOS regulatory systems in apoE
−/−
mice. Aortic caveolin-1 protein, an inhibitor of endothelial NOS, was also increased in these mice by 2.0-fold and correlated positively with systolic BPV in the very-low-frequency band. Rosuvastatin treatment corrected the hemodynamic and caveolin-1 expression changes despite persisting elevated plasma cholesterol levels.

Conclusions—

Rosuvastatin decreases caveolin-1 expression and promotes NOS function in apoE
−/−
, dyslipidemic mice in vivo, with concurrent improvements in BPV and HRV. This highlights the beneficial effects of rosuvastatin on cardiovascular function beyond those attributed to lipid lowering.
Antiapoptotic Effect of Endothelin-1 in Rat Cardiomyocytes In Vitro
Authors: Ogata Yukiyo , Takahashi Masafumi , Ueno Shuichi , Takeuchi Koichi , Okada Takashi , Mano Hiroyuki , Ookawara Shigeo , Ozawa Keiya , Berk Bradford C. , Ikeda Uichi , Shimada Kazuyuki , Kobayashi Eiji
Published: May 2003

Apoptosis of cardiac myocytes is thought to be a feature of many pathological disorders, including congestive heart failure (CHF) and ischemic heart disease (IHD). Because recent investigations indicate that endothelin-1 (ET-1) plays an important role in CHF and IHD, we investigated the effect of ET-1 on cardiomyocyte apoptosis. The presence of apoptosis in rat cardiomyocytes (H9c2 and neonatal) was evaluated by morphological criteria, electrophoresis of DNA fragments, 4′,6′-diamidine-2′-phenylindole staining, and TUNEL analysis. ET-1, but not angiotensin II, prevented apoptosis induced by serum deprivation via ET
A
receptors in a dose-dependent manner (1 to 100 nmol/L). ET-1 also prevented cytochrome
c
release from mitochondria to the cytosol. The use of specific pharmacological inhibitors demonstrated that the antiapoptotic effect of ET-1 was mediated through a tyrosine kinase pathway (genistein and AG490) but not through protein kinase C (PKC; calphostin C), mitogen-activated protein kinases (PD98059 and SB203580), or PKA (KT5270) pathways. Adenovirus-mediated gene transfer of kinase-inactive (KI) c-Src reversed the antiapoptotic effect of ET-1. We further investigated whether Bcl-x
L
, an antiapoptotic molecule, would be upregulated by using a luciferase-based reporter system. ET-1 upregulated Bcl-x
L
, and this upregulation was inhibited by genistein or AG490 but not by calphostin C. The experiments with KI mutants for various tyrosine kinases revealed that c-Src and Pyk2 (but not JAK1, Jak2, Syk, and Tec) are involved in ET-1–induced upregulation of Bcl-x
L
expression. These findings suggest that ET-1 prevents apoptosis in cardiac myocytes through the ET
A
receptor and the subsequent c-Src/Bcl-x
L
–dependent pathway.
Prediction of Genetic Risk for Hypertension
Authors: Izawa Hideo , Yamada Yoshiji , Okada Taro , Tanaka Masashi , Hirayama Haruo , Yokota Mitsuhiro
Published: May 2003

Although genetic epidemiological studies have suggested that several genetic variants increase the risk for hypertension, the genes that underlie genetic susceptibility to this condition remain to be identified definitively. Large-scale association studies that examine many gene polymorphisms simultaneously are required to predict genetic risk for hypertension. The population of the present study comprised 1940 unrelated Japanese individuals, including 1067 subjects with hypertension (574 men, 493 women) and 873 controls (533 men, 340 women). The genotypes for 33 single nucleotide polymorphisms of 27 candidate genes were determined with a fluorescence- or colorimetry-based allele-specific DNA primer-probe assay system. Multivariate logistic regression analysis with adjustment for age, body mass index, and the prevalence of smoking, diabetes mellitus, hypercholesterolemia, and hyperuricemia revealed that 2 polymorphisms (825C→T in the G protein β3 subunit gene and 190G→A in the CC chemokine receptor 2 gene) were significantly associated with hypertension in men and that one polymorphism (−238G→A in the tumor necrosis factor α gene) was significantly associated with hypertension in women. These results suggest that 2 and 1 genes may be susceptibility loci for hypertension in Japanese men and women, respectively, and that genotyping of these polymorphisms may prove informative for prediction of the genetic risk for hypertension.
Aldosterone Regulates the Na-K-2Cl Cotransporter in Vascular Smooth Muscle
Authors: Jiang Gengru , Cobbs Scott , Klein Janet D. , O’Neill W. Charles
Published: May 2003

Aldosterone increases cation transport and contractility of vascular smooth muscle, but the specific transporter involved and how it is linked to smooth muscle tone is unknown. Because the Na-K-2Cl cotransporter (NKCC1) contributes to vascular smooth muscle contraction and is regulated by vasoactive compounds, we sought to determine whether this transporter is a target of aldosterone in rat aorta. Treatment of adrenalectomized rats with aldosterone for 7 days resulted in a 63% increase in NKCC1 activity as measured by bumetanide-sensitive efflux of
86
Rb
+
. Treatment of normal aortas in culture with aldosterone for 3 and 7 days resulted in 29% and 47% increases in NKCC1 activity, respectively. Aldosterone had no acute effect on
86
Rb
+
efflux. Stimulation of NKCC1 was blocked by spironolactone, a mineralocorticoid receptor antagonist, but not by RU38486, a glucocorticoid receptor antagonist. Aldosterone did not augment the stimulation of NKCC1 by phenylephrine and did not increase NKCC1 mRNA as determined by real-time polymerase chain reaction. We conclude that aldosterone regulates the Na-K-2Cl cotransporter in vascular smooth muscle through classic mineralocorticoid receptors but not through changes in the abundance of NKCC1 mRNA. This could account for the increase in Na
+
, K
+
, and Cl
−
fluxes previously observed in vascular smooth muscle from mineralocorticoid-treated animals and may contribute to increased vascular tone.
Cyclosporin A Disrupts Bradykinin Signaling Through Superoxide
Authors: Vetter Michael , Chen Zi-Jiang , Chang Geen-Dong , Che Danian , Liu Shiguo , Chang Chung-Ho
Published: May 2003

Cyclosporin A (CsA) is used to reduce transplant rejection rates. Chronic use, however, has a destructive toxic effect on the kidney, resulting in hypertension. In this study, we investigated the effects of CsA treatment on the bradykinin/soluble guanylate cyclase signaling cascade and the involvement of superoxide in LLC-PK1 porcine kidney proximal tubule cells. Treatment with 1 μmol/L CsA for 24 hours increased basal cGMP levels by 41%, whereas CsA inhibited bradykinin-stimulated cGMP production by 26%. Western blotting showed increased expression of eNOS, but no other protein in the bradykinin/soluble guanylate cyclase (sGC) pathway was affected. Using lucigenin-dependent chemiluminescence, we found that CsA treatment significantly increased superoxide production. Production of O
2
−
was not significantly reduced by 10 μmol/L oxypurinol or 30 μmol/L ketoconazole. However, it was inhibited by the NADPH oxidase inhibitor diphenyleneiodonium chloride (10 μmol/L) as well as the O
2
−
scavenger superoxide dismutase (SOD) (100 U). On treatment with 50 μmol/L quercetin, 10 mmol/L
N
-acetyl-cysteine, both antioxidants, as well as the O
2
−
scavenger Tiron (10 mmol/L), concomitant with 1 μmol/L CsA for 24 hours the activation of cGMP production, was restored in combination with a reduction in O
2
−
. Incubation with 100 μmol/L menadione, a reactive oxygen generator, and 10 nmol/L bradykinin showed similar effects on the level of cGMP as with CsA. CsA treatment was found to increase nitrotyrosine levels. These findings suggest that CsA activates a NADPH oxidase that releases O
2
−
and disrupts the bradykinin/soluble guanylate cyclase pathway, probably by binding with NO to form peroxynitrite (ONOO
−
).
Myocardin Is a Key Regulator of CArG-Dependent Transcription of Multiple Smooth Muscle Marker Genes
Authors: Yoshida Tadashi , Sinha Sanjay , Dandré Frédéric , Wamhoff Brian R. , Hoofnagle Mark H. , Kremer Brandon E. , Wang Da-Zhi , Olson Eric N. , Owens Gary K.
Published: May 2003

The interactions between serum response factor (SRF) and CArG elements are critical for smooth muscle cell (SMC) marker gene transcription. However, the mechanisms whereby SRF, which is expressed ubiquitously, contributes to SMC-specific transcription are unknown. Myocardin was recently cloned as a coactivator of SRF in the heart, but its role in regulating CArG-dependent expression of SMC differentiation marker genes has not been clearly elucidated. In this study, we examined the expression and the function of myocardin in SMCs. In adult mice, myocardin mRNA was expressed in multiple smooth muscle (SM) tissues including the aorta, bladder, stomach, intestine, and colon, as well as the heart. Myocardin was also expressed in cultured rat aortic SMCs and A404 SMC precursor cells. Of particular interest, expression of myocardin was induced during differentiation of A404 cells, although it was not expressed in parental P19 cells from which A404 cells were derived. Cotransfection studies in SMCs revealed that myocardin induced the activity of multiple SMC marker gene promoters including SM α-actin, SM-myosin heavy chain, and SM22α by 9- to 60-fold in a CArG-dependent manner, whereas myocardin short interfering RNA markedly decreased activity of these promoters. Moreover, adenovirus-mediated overexpression of a dominant-negative form of myocardin significantly suppressed expression of endogenous SMC marker genes, whereas adenovirus-mediated overexpression of wild-type myocardin increased expression. Taken together, results provide compelling evidence that myocardin plays a key role as a transcriptional coactivator of SMC marker genes through CArG-dependent mechanisms.
Hypoxia Enhances Ecto-5′-Nucleotidase Activity and Cell Surface Expression in Endothelial Cells
Authors: Ledoux S. , Runembert I. , Koumanov K. , Michel J.B. , Trugnan G. , Friedlander G.
Published: May 2003

Extracellular adenosine production by the glycosyl-phosphatidyl-inositol-anchored Ecto-5′-Nucleotidase plays an important role in the defense against hypoxia, particularly in the intravascular space. The present study was designed in order to elucidate the mechanisms underlying hypoxia-induced stimulation of Ecto-5′-Nucleotidase in endothelial cells. For this purpose, aortic endothelial cells (SVARECs) were submitted to hypoxic gas mixture. Hypoxia (0% O
2
for 18 hours) induced a 2-fold increase of Ecto-5′-Nucleotidase activity (V
max
19.78±0.53 versus 8.82±1.12 nmol/mg protein per min), whereas mRNA abundance and total amount of the protein were unmodified. By contrast, hypoxia enhanced cell surface expression of Ecto-5′-Nucleotidase, as evidenced both by biotinylation and immunostaining. This effect was accompanied by a decrease of Ecto-5′-Nucleotidase endocytosis, without modification of Ecto-5′-Nucleotidase association with detergent-resistant membranes. Finally, whereas cholesterol content was unmodified, hypoxia induced a time-dependent increase of saturated fatty acids in SVARECs, which was reversed by reoxygenation, in parallel to Ecto-5′-Nucleotidase stimulation. Incubation of normoxic cells with palmitic acid enhanced Ecto-5′-Nucleotidase activity and cell surface expression. In conclusion, hypoxia enhances cell surface expression of Ecto-5′-Nucleotidase in endothelial cells. This effect could be supported by a decrease of Ecto-5′-Nucleotidase endocytosis through modification of plasma membrane fatty acid composition.
Increased Fibronectin Deposition in Embryonic Hearts of Retinol-Binding Protein–Null Mice
Authors: Wendler Christopher C. , Schmoldt Angela , Flentke George R. , Case Lauren C. , Quadro Loredana , Blaner William S. , Lough John , Smith Susan M.
Published: May 2003

Precise regulation of retinoid levels is critical for normal heart development. Retinol-binding protein (RBP), an extracellular retinol transporter, is strongly secreted by cardiogenic endoderm. This study addresses whether RBP gene ablation affects heart development. Despite exhibiting an >85% decrease in serum retinol, adult RBP-null mice are viable, breed, and have normal vision when maintained on a vitamin A–sufficient diet. Comparison of RBP-null with wild-type (WT) hearts from embryos at day 9.0 (E9.0) through E12.5 revealed an RBP-null phenotype similar to that of other retinoid-deficient models. At an early stage, RBP-null hearts display retarded trabecular development, which recovers by E9.5. This is accompanied at E9.5 and E10.5 by precocious differentiation of subepicardial cardiac myocytes. Most remarkably, RBP-null hearts display augmented deposition of fibronectin protein in the cardiac jelly at E9.0 through E10.5 and in the outflow tract at E12.5. This phenomenon, which was detected by immunohistochemistry and Western blotting without increased fibronectin transcript levels, is accompanied by increased numbers of mesenchymal cells in the outflow tract but not in the atrioventricular canal. RBP-null cardiac myocytes, especially in the subepicardial layer, display increased cell proliferation. This phenotype may present a model of subclinical retinoid insufficiency characterized by alteration of an extracellular matrix component and altered cellular differentiation and proliferation, changes that may have functional consequences for adult cardiac function. This murine model may have relevance to fetal development in human populations with inadequate retinoid intake.
Ca
2+
Uptake by the Sarcoplasmic Reticulum in Ventricular Myocytes of the
SERCA2
b/b
Mouse Is Impaired at Higher Ca
2+
Loads Only
Authors: Antoons Gudrun , Ver Heyen Mark , Raeymaekers Luc , Vangheluwe Peter , Wuytack Frank , Sipido Karin R.
Published: May 2003

SERCA2a is the cardiac-specific isoform of Ca
2+
-ATPase of the sarcoplasmic reticulum (SR). A reduction of SERCA2a has been implicated in the contractile dysfunction of heart failure, and partial knockout of the SERCA2 gene (
Atp2a2
+/−
mice) reiterated many of the features of heart failure. Yet, mice with a mutation of
Atp2a2
, resulting in full suppression of the SERCA2a isoform and expression of the SERCA2b isoform only (
SERCA2
b/b
), showed only moderate functional impairment, despite a reduction by 40% of the SERCA2 protein levels. We examined in more detail the Ca
2+
handling in isolated cardiac myocytes from
SERCA2
b/b
. At 0.25 Hz stimulation, the amplitude of the [Ca
2+
]
i
transients, SR Ca
2+
content, diastolic [Ca
2+
]
i
, and density of
I
CaL
were comparable between WT and
SERCA2
b/b
. However, the decline of [Ca
2+
]
i
was slower (t
1/2
154±7 versus 131±5 ms;
P
<0.05). Reducing the amplitude of the [Ca
2+
]
i
transient (eg, SR depletion), removed the differences in [Ca
2+
]
i
decline. In contrast, increasing the Ca
2+
load revealed pronounced reduction of SR Ca
2+
uptake at high [Ca
2+
]
i
. There was no increase in Na
+
-Ca
2+
exchange protein or function. Theoretical modeling indicated that in the
SERCA2
b/b
mouse, the higher Ca
2+
affinity of SERCA2b partially compensates for the 40% reduction of SERCA expression. The lack of SR depletion in the
SERCA2
b/b
may also be related to the absence of upregulation of Na
+
-Ca
2+
exchange. We conclude that for SERCA isoforms with increased affinity for Ca
2+
, a reduced expression level is better tolerated as Ca
2+
uptake and storage are impaired only at higher Ca
2+
loads.
Transgenic CaMKIIδ
C
Overexpression Uniquely Alters Cardiac Myocyte Ca
2+
Handling
Authors: Maier Lars S. , Zhang Tong , Chen Lu , DeSantiago Jaime , Brown Joan Heller , Bers Donald M.
Published: May 2003

Ca
2+
/calmodulin-dependent protein kinase II (CaMKII) δ is the predominant cardiac isoform, and the δ
C
splice variant is cytoplasmic. We overexpressed CaMKIIδ
C
in mouse heart and observed dilated heart failure and altered myocyte Ca
2+
regulation in 3-month-old CaMKIIδ
C
transgenic mice (TG) versus wild-type littermates (WT). Heart/body weight ratio and cardiomyocyte size were increased about 2-fold in TG versus WT. At 1 Hz, twitch shortening, [Ca
2+
]
i
transient amplitude, and diastolic [Ca
2+
]
i
were all reduced by ≈50% in TG versus WT. This is explained by >50% reduction in SR Ca
2+
content in TG versus WT. Peak Ca
2+
current (
I
Ca
) was slightly increased, and action potential duration was prolonged in TG versus WT. Despite lower SR Ca
2+
load and diastolic [Ca
2+
]
i
, fractional SR Ca
2+
release was increased and resting spontaneous SR Ca
2+
release events (Ca
2+
sparks) were doubled in frequency in TG versus WT (with prolonged width and duration, but lower amplitude). Enhanced Ca
2+
spark frequency was also seen in TG at 4 weeks (before heart failure onset). Acute CaMKII inhibition normalized Ca
2+
spark frequency and
I
Ca
, consistent with direct CaMKII activation of ryanodine receptors (and
I
Ca
) in TG. The rate of [Ca
2+
]
i
decline during caffeine exposure was faster in TG, indicating enhanced Na
+
-Ca
2+
exchange function (consistent with protein expression measurements). Enhanced diastolic SR Ca
2+
leak (via sparks), reduced SR Ca
2+
-ATPase expression, and increased Na
+
-Ca
2+
exchanger explain the reduced diastolic [Ca
2+
]
i
and SR Ca
2+
content in TG. We conclude that CaMKIIδ
C
overexpression causes acute modulation of excitation-contraction coupling, which contributes to heart failure.
Blockade of Vascular Smooth Muscle Cell Proliferation and Intimal Thickening After Balloon Injury by the Sulfated Oligosaccharide PI-88
Authors: Francis Douglas J. , Parish Christopher R. , McGarry Mark , Santiago Fernando S. , Lowe Harry C. , Brown Kathryn J. , Bingley John A. , Hayward Ian P. , Cowden William B. , Campbell Julie H. , Campbell Gordon R. , Chesterman Colin N. , Khachigian Levon M.
Published: May 2003

Percutaneous transluminal coronary angioplasty is a frequently used interventional technique to reopen arteries that have narrowed because of atherosclerosis. Restenosis, or renarrowing of the artery shortly after angioplasty, is a major limitation to the success of the procedure and is due mainly to smooth muscle cell accumulation in the artery wall at the site of balloon injury. In the present study, we demonstrate that the antiangiogenic sulfated oligosaccharide, PI-88, inhibits primary vascular smooth muscle cell proliferation and reduces intimal thickening 14 days after balloon angioplasty of rat and rabbit arteries. PI-88 reduced heparan sulfate content in the injured artery wall and prevented change in smooth muscle phenotype. However, the mechanism of PI-88 inhibition was not merely confined to the antiheparanase activity of this compound. PI-88 blocked extracellular signal-regulated kinase-1/2 (ERK1/2) activity within minutes of smooth muscle cell injury. It facilitated FGF-2 release from uninjured smooth muscle cells in vitro, and super-released FGF-2 after injury while inhibiting ERK1/2 activation. PI-88 inhibited the decrease in levels of FGF-2 protein in the rat artery wall within 8 minutes of injury. PI-88 also blocked injury-inducible ERK phosphorylation, without altering the clotting time in these animals. Optical biosensor studies revealed that PI-88 potently inhibited (
K
i
10.3 nmol/L) the interaction of FGF-2 with heparan sulfate. These findings show for the first time the capacity of this sulfated oligosaccharide to directly bind FGF-2, block cellular signaling and proliferation in vitro, and inhibit injury-induced smooth muscle cell hyperplasia in two animal models. As such, this study demonstrates a new role for PI-88 as an inhibitor of intimal thickening after balloon angioplasty. The full text of this article is available online at http://www.circresaha.org.
Smoking and the Risk of Hemorrhagic Stroke in Men
Authors: Kurth Tobias , Kase Carlos S. , Berger Klaus , Schaeffner Elke S. , Buring Julie E. , Gaziano J. Michael
Published: May 2003

Background and Purpose—

Smoking is an established risk factor for ischemic stroke and subarachnoid hemorrhage (SAH), but the impact of smoking on intracerebral hemorrhage (ICH) is less clear.

Methods—

Prospective cohort study among 22 022 US male physicians participating in the Physicians’ Health Study. Incidence of stroke was measured by self-report and confirmed by medical record review. We used Cox proportional-hazards models to evaluate the association of smoking with risk of total hemorrhagic stroke, ICH, and SAH. We categorized smoking into 4 groups: never, past, or current smokers of <20 or of ≥20 cigarettes per day.

Results—

During 17.8 years of follow-up, 108 ICHs and 31 SAHs occurred. Never smokers and past smokers had equal rates of ICH and SAH. Current smokers of <20 cigarettes per day had multivariable-adjusted relative risks of 1.65 (95% CI, 0.61 to 4.50) for total hemorrhagic stroke, 1.60 (95% CI, 0.50 to 5.07) for ICH, and 1.75 (95% CI, 0.24 to 13.09) for SAH when compared with never smokers. Current smokers of ≥20 cigarettes had relative risks of 2.36 (95% CI, 1.38 to 4.02) for total hemorrhagic stroke, 2.06 (95% CI, 1.08 to 3.96) for ICH, and 3.22 (95% CI, 1.26 to 8.18) for SAH when compared with never smokers.

Conclusions—

This prospective study suggests an increased risk of total hemorrhagic stroke, ICH, and SAH in current cigarette smokers with a graded increase in risk that depended on how many cigarettes were smoked. The effect of smoking on ICH is of about the same magnitude as the effect of smoking on ischemic stroke. Our results add to the multiple health benefits that can be accrued by abstaining from cigarette smoking.