bluuebunny/crossref_metadata_2025 huggingface dataset:
On the phase identification of dc magnetron sputtered Pt–Ru alloy thin films
Authors: Warren A. P. , Todi R. M. , Yao B. , Barmak K. , Sundaram K. B. , Coffey K. R.
Published: September 2008

The microstructure and the electronic work function of Pt–Ru alloy thin films spanning the compositional range from pure Pt to pure Ru were investigated. Nominally 50nm thick films were cosputtered from elemental targets in an ultrahigh vacuum chamber. X-ray reflectivity and Rutherford backscattering spectroscopy were used to determine the film thicknesses and compositions. The electronic work function of the alloy film samples was determined by analysis of the capacitance-voltage characteristics of films deposited as part of a metal-oxide-semiconductor capacitor structure and found to range from 4.8eV for pure Ru to 5.2eV for pure Pt. To better understand the variation in work function for the intermediate compositions, the films were characterized by transmission electron microscopy and x-ray and electron diffractions. A notable increase in the compositional range of the hexagonal close packed (hcp) phase was observed, suggesting a metastable extension of the hcp phase stability as compared to bulk Pt–Ru alloys. The steepest change in the electronic work function for the intermediate alloy compositions coincided with a rapid change in the c∕a ratio of the hcp phase.
Unique lack of chemical reactivity for 2,3-dimethyl-2-butene on a Si(100)-2×1 surface
Authors: Madachik Mark R. , Teplyakov Andrew V.
Published: September 2008

Adsorption of 2,3-dimethyl-2-butene on Si(100)-2×1 has been studied by a combination of multiple internal reflection Fourier transform infrared spectroscopy and computational investigations implementing density functional theory (DFT). Since the previously studied olefins have been shown to form a di-σ product on this surface following [2+2] cycloaddition, it was also initially expected for 2,3-dimethyl-2-butene. Infrared spectra taken at 100K show that 2,3-dimethyl-2-butene adsorbs on the surface molecularly at this temperature. Heating the surface to room temperature left no indication of a chemisorbed product. Large doses at room temperature did not produce any observable absorption bands in the infrared spectrum, indicating that [2+2] cycloaddition of 2,3-dimethyl-2-butene does not occur. This assessment was verified by the Auger electron spectroscopy studies confirming that neither room temperature exposure nor annealing to 800K produced any carbon remaining on this surface. These experimental observations of the absence of a chemical reaction between an olefin and a very reactive silicon surface were substantiated by DFT investigation of the adsorption kinetics. The formation of two possible π-bonded precursors was considered, and the energies required to form the di-σ-bonded product from either one of these precursors were predicted to be substantially higher than the desorption barrier. Thus, 2,3-dimethyl-2-butene is a unique olefin that is very inert with respect to the Si(100)-2×1 surface, making it a desirable carrier gas or a ligand in the precursor molecules in a number of deposition processes involving silicon substrates.
Pulsed dc self-sustained magnetron sputtering
Authors: Wiatrowski A. , Posadowski W. M. , Radzimski Z. J.
Published: September 2008

The magnetron sputtering has become one of the commonly used techniques for industrial deposition of thin films and coatings due to its simplicity and reliability. At standard magnetron sputtering conditions (argon pressure of ∼0.5Pa) inert gas particles (necessary to sustain discharge) are often entrapped in the deposited films. Inert gas contamination can be eliminated during the self-sustained magnetron sputtering (SSS) process, where the presence of the inert gas is not a necessary requirement. Moreover the SSS process that is possible due to the high degree of ionization of the sputtered material also gives a unique condition during the transport of sputtered particles to the substrate. So far it has been shown that the self-sustained mode of magnetron operation can be obtained using dc powering (dc-SSS) only. The main disadvantage of the dc-SSS process is its instability related to random arc formation. In such case the discharge has to be temporarily extinguished to prevent damaging both the magnetron source and power supply. The authors postulate that pulsed powering could protect the SSS process against arcs, similarly to reactive pulsed magnetron deposition processes of insulating thin films. To put this concept into practice, (i) the high enough plasma density has to be achieved and (ii) the type of pulsed powering has to be chosen taking plasma dynamics into account. In this article results of pulsed dc self-sustained magnetron sputtering (pulsed dc-SSS) are presented. The planar magnetron equipped with a 50mm diameter and 6mm thick copper target was used during the experiments. The maximum target power was about 11kW, which corresponded to the target power density of ∼560W∕cm2. The magnetron operation was investigated as a function of pulse frequency (20–100kHz) and pulse duty factor (50%–90%). The discharge (argon) extinction pressure level was determined for these conditions. The plasma emission spectra (400–410nm range) and deposition rates were observed for both dc and pulsed dc self-sustained sputtering processes. The pulse characteristics of the voltage and current of the magnetron source during pulsed dc-SSS operation are shown. The presented results illustrate that a stable pulsed dc-SSS process can be obtained at a pulsing frequency in the range of 60–90kHz and duty factor of 80%–90%.
Feedback control of HfO2 etch processing in inductively coupled Cl2/N2/Ar plasmas
Authors: Lin Chaung , Leou Keh-Chyang , Li Ting-Chieh , Lee Lurng-Shehng , Tzeng Pei-Jer
Published: September 2008

The etch rate of HfO2 etch processing has been feedback controlled in inductively coupled Cl2/N2/Ar plasmas. The ion current and the root mean square rf voltage on the wafer stage, which are measured using a commercial impedance meter connected to the wafer stage, are chosen as controlled variables because the positive-ion flux and ion energy incident upon the wafer surface are the key factors that determine the etch rate. Two 13.56 MHz rf generators are used to adjust the inductively coupled plasma power and bias power which control ion density and ion energy, respectively. The adopted HfO2 etch processing used rather low rf voltage. The ion-current value obtained by the power/voltage method is underestimated, so the neural-network model was developed to assist estimating the correct ion-current value. The experimental results show that the etch-rate variation of the closed-loop control is smaller than that of the open-loop control. However, the first wafer effect cannot be eliminated using closed-loop control and thus to achieve a constant etch rate, the chamber-conditioning procedure is required in this etch processing.
Local supply of gas in vacuum: Application to a field ion source
Authors: Descoins Marion , Hammadi Zoubida , Morin Roger
Published: September 2008

The flow of hydrogen, helium, and nitrogen through a millimeter long and micrometer size annulus capillary from a high pressure chamber to a low pressure chamber is measured in a wide pressure range. The corresponding gas conductance is deduced. Molecular, transition, and viscous regimes are observed. The local supply of gas strongly increases with pressure in the viscous regime up to a regime controlled by capillary exit loss. Based on such a geometry, the gas supply to a field ion source with a coaxial structure is shown to be increased by more than three orders of magnitude compared to a conventional supply.
Unsupervised Natural Experience Rapidly Alters Invariant Object Representation in Visual Cortex
Authors: Li Nuo , DiCarlo James J.
Published: September 2008

Object recognition is challenging because each object produces myriad retinal images. Responses of neurons from the inferior temporal cortex (IT) are selective to different objects, yet tolerant (“invariant”) to changes in object position, scale, and pose. How does the brain construct this neuronal tolerance? We report a form of neuronal learning that suggests the underlying solution. Targeted alteration of the natural temporal contiguity of visual experience caused specific changes in IT position tolerance. This unsupervised temporal slowness learning (UTL) was substantial, increased with experience, and was significant in single IT neurons after just 1 hour. Together with previous theoretical work and human object perception experiments, we speculate that UTL may reflect the mechanism by which the visual stream builds and maintains tolerant object representations.
Northern Hemisphere Controls on Tropical Southeast African Climate During the Past 60,000 Years
Authors: Tierney Jessica E. , Russell James M. , Huang Yongsong , Damsté Jaap S. Sinninghe , Hopmans Ellen C. , Cohen Andrew S.
Published: September 2008

The processes that control climate in the tropics are poorly understood. We applied compound-specific hydrogen isotopes (δD) and the TEX
86
(tetraether index of 86 carbon atoms) temperature proxy to sediment cores from Lake Tanganyika to independently reconstruct precipitation and temperature variations during the past 60,000 years. Tanganyika temperatures follow Northern Hemisphere insolation and indicate that warming in tropical southeast Africa during the last glacial termination began to increase ∼3000 years before atmospheric carbon dioxide concentrations. δD data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial-scale events recorded in Northern Hemisphere monsoonal climate records. This implies that precipitation in tropical southeast Africa is more strongly controlled by changes in Indian Ocean sea surface temperatures and the winter Indian monsoon than by migration of the Intertropical Convergence Zone.
Niche Partitioning Increases Resource Exploitation by Diverse Communities
Authors: Finke Deborah L. , Snyder William E.
Published: September 2008

Classical ecological theory suggests that the coexistence of consumer species is fostered by resource-use differences, leading to greater resource use in communities with more species. However, explicit empirical support for this idea is lacking, because resource use by species is generally confounded with other species-specific attributes. We overcame this obstacle by co-opting behavioral plasticity in food choice among a group of animal consumers, allowing us to manipulate patterns of resource use while controlling for the effects of species identity and diversity. Within an aphid-parasitoid-radish community, we created a fully factorial manipulation of consumer resource-use breadth (specialist versus generalist) and species diversity (one versus three species) and found that resource exploitation improved with greater specialist, but not generalist, diversity. Therefore, resource partitioning, and not diversity per se, fostered greater overall resource consumption in our multispecies consumer communities.
Illuminating the Details of Deep Time
Authors: O'Connor Ralph J.
Published: September 2008

Worlds Before Adam
. The Reconstruction of Geohistory in the Age of Reform.
By Martin J. S. Rudwick
. University of Chicago Press, Chicago, 2008. 638 pp. $49, £25.50. ISBN 9780226731285.

The author examine a selection of influential scientific debates on geologic topics between 1820 and 1845, some of which were focused on the details of particular moments in what all agreed were the long histories of Earth and life while others addressed putative causes of the patterns.
A Mutation in Hairless Dogs Implicates
FOXI3
in Ectodermal Development
Authors: Drögemüller Cord , Karlsson Elinor K. , Hytönen Marjo K. , Perloski Michele , Dolf Gaudenz , Sainio Kirsi , Lohi Hannes , Lindblad-Toh Kerstin , Leeb Tosso
Published: September 2008

Mexican and Peruvian hairless dogs and Chinese crested dogs are characterized by missing hair and teeth, a phenotype termed canine ectodermal dysplasia (CED). CED is inherited as a monogenic autosomal semidominant trait. With genomewide association analysis we mapped the CED mutation to a 102–kilo–base pair interval on chromosome 17. The associated interval contains a previously uncharacterized member of the forkhead box transcription factor family (FOXI3), which is specifically expressed in developing hair and teeth. Mutation analysis revealed a frameshift mutation within the FOXI3 coding sequence in hairless dogs. Thus, we have identified FOXI3 as a regulator of ectodermal development.
Scientists Under Siege
Authors: Runkle Deborah C.
Published: September 2008

The Animal Research War
.
By P. Michael Conn and James V. Parker
. Palgrave Macmillan, New York, 2008. 219 pp. $34.95, £22.99. ISBN 9780230600140.

This exposé of tactics used by animal rights extremists spotlights the efforts of those who wish to abolish all experimental work with animals.
Complete DNA Sequences of Two Oka Strain Varicella-Zoster Virus Genomes
Authors: Tillieux Sueli L. , Halsey Wendy S. , Thomas Elizabeth S. , Voycik John J. , Sathe Ganesh M. , Vassilev Ventzislav
Published: September 2008

Varicella-zoster virus (VZV) is a herpesvirus and is the causative agent of chicken pox (varicella) and shingles (herpes zoster). Active immunization against varicella became possible with the development of live attenuated varicella vaccine. The Oka vaccine strain was isolated in Japan from a child who had typical varicella, and it was then attenuated by serial passages in cell culture. Several manufacturers have obtained this attenuated Oka strain and, following additional passages, have developed their own vaccine strains. Notably, the vaccines Varilrix and Varivax are produced by GlaxoSmithKline Biologicals and Merck & Co., Inc., respectively. Both vaccines have been well studied in terms of safety and immunogenicity. In this study, we report the complete nucleotide sequence of the Varilrix (Oka-V
GSK
) and Varivax (Oka-V
Merck
) vaccine strain genomes. Their genomes are composed of 124,821 and 124,815 bp, respectively. Full genome annotations covering the features of Oka-derived vaccine genomes have been established for the first time. Sequence analysis indicates 36 nucleotide differences between the two vaccine strains throughout the entire genome, among which only 14 are involved in unique amino acid substitutions. These results demonstrate that, although Oka-V
GSK
and Oka-V
Merck
vaccine strains are not identical, they are very similar, which supports the clinical data showing that both vaccines are well tolerated and elicit strong immune responses against varicella.
Incorporation of Membrane-Anchored Flagellin into Influenza Virus-Like Particles Enhances the Breadth of Immune Responses
Authors: Wang Bao-Zhong , Quan Fu-Shi , Kang Sang-Moo , Bozja Jadranka , Skountzou Ioanna , Compans Richard W.
Published: September 2008

We have designed a membrane-anchored form of the Toll-like receptor 5 ligand flagellin, the major proinflammatory determinant of enteropathogenic
Salmonella
, which was found to be glycosylated and expressed on cell surfaces. A chimeric influenza virus-like particle (cVLP) vaccine candidate containing A/PR8/34 (H
1
N
1
) hemagglutinin (HA), matrix protein (M1), and the modified flagellin as a molecular adjuvant was produced. The immunogenicity, including the serum antibody levels and cellular immune responses, and the protective efficacy against homologous and heterologous live virus challenge of the resulting VLPs were tested after intramuscular administration in a mouse model. The results demonstrated that flagellin-containing VLPs elicited higher specific immunoglobulin G (IgG) responses than standard HA and M1 VLPs, indicating the adjuvant effect of flagellin. Enhanced IgG2a and IgG2b but not IgG1 responses were observed with flagellin-containing VLPs, illuminating the activation of Th1 class immunity. The adjuvant effects of flagellin were also reflected by enhanced specific cellular responses revealed by the secretion of cytokines by freshly isolated splenocyte cultures when stimulated with pools of major histocompatibility complex class I or II peptides. When immunized mice were challenged with homologous live PR8 virus, complete protection was observed for both the standard and cVLP groups. However, when a heterosubtypic A/Philippines (H
3
N
2
) virus was used for challenge, all of the standard VLP group lost at least 25% of body weight, reaching the experimental endpoint. In contrast, for the cVLP group, 67% of mice survived the challenge infection. These results reveal that cVLPs designed by incorporating flagellin as a membrane-anchored adjuvant induce enhanced cross-protective heterosubtypic immune responses. They also indicate that such cVLP vaccines are a promising new approach for protection against pandemic influenza viruses.
Pathogenicity and Vaccine Efficacy of Different Clades of Asian H5N1 Avian Influenza A Viruses in Domestic Ducks
Authors: Kim Jeong-Ki , Seiler Patrick , Forrest Heather L. , Khalenkov Alexey M. , Franks John , Kumar Mahesh , Karesh William B. , Gilbert Martin , Sodnomdarjaa R. , Douangngeun Bounlom , Govorkova Elena A. , Webster Robert G.
Published: September 2008

Waterfowl represent the natural reservoir of all subtypes of influenza A viruses, including H5N1. Ducks are especially considered major contributors to the spread of H5N1 influenza A viruses because they exhibit diversity in morbidity and mortality. Therefore, as a preventive strategy against endemic as well as pandemic influenza, it is important to reduce the spread of H5N1 influenza A viruses in duck populations. Here, we describe the pathogenicity of dominant clades (clades 1 and 2) of H5N1 influenza A viruses circulating in birds in Asia. Four representatives of dominant clades of the viruses cause symptomatic infection but lead to different profiles of lethality in domestic ducks. We also demonstrate the efficacy, cross-protectiveness, and immunogenicity of three different inactivated oil emulsion whole-virus H5 influenza vaccines (derived by implementing reverse genetics) to the viruses in domestic ducks. A single dose of the vaccines containing 1 μg of hemagglutinin protein provides complete protection against a lethal A/Duck/Laos/25/06 (H5N1) influenza virus challenge, with no evidence of morbidity, mortality, or shedding of the challenge virus. Moreover, two of the three vaccines achieved complete cross-clade or cross-subclade protection against the heterologous avian influenza virus challenge. Interestingly, the vaccines induce low or undetectable titers of hemagglutination inhibition (HI), cross-HI, and/or virus neutralization antibodies. The mechanism of complete protection in the absence of detectable antibody responses remains an open question.
Mouse APOBEC3 Restricts Friend Leukemia Virus Infection and Pathogenesis In Vivo
Authors: Takeda Eri , Tsuji-Kawahara Sachiyo , Sakamoto Mayumi , Langlois Marc-André , Neuberger Michael S. , Rada Cristina , Miyazawa Masaaki
Published: September 2008

Several members of the apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like complex 3 (APOBEC3) family in primates act as potent inhibitors of retroviral replication. However, lentiviruses have evolved mechanisms to specifically evade host APOBEC3. Likewise, murine leukemia viruses (MuLV) exclude mouse APOBEC3 from the virions and cleave virion-incorporated APOBEC3. Although the betaretrovirus mouse mammary tumor virus has been shown to be susceptible to mouse APOBEC3, it is not known if APOBEC3 has a physiological role in restricting more widely distributed and long-coevolved mouse gammaretroviruses. The pathogenicity of Friend MuLV (F-MuLV) is influenced by several host genes: some directly restrict the cell entry or integration of the virus, while others influence the host immune responses. Among the latter, theRfv3gene has been mapped to chromosome 15 in the vicinity of theAPOBEC3locus. Here we have shown that polymorphisms at the mouseAPOBEC3locus indeed influence F-MuLV replication and pathogenesis: theAPOBEC3alleles of F-MuLV-resistant C57BL/6 and -susceptible BALB/c mice differ in their sequences and expression levels in the hematopoietic tissues and in their abilities to restrict F-MuLV replication both in vitro and in vivo. Furthermore, upon infection with the pathogenic Friend virus complex, (BALB/c × C57BL/6)F1mice displayed an exacerbated erythroid cell proliferation when the mice carried a targeted disruption of the C57BL/6-derivedAPOBEC3allele. These results indicate, for the first time, that mouse APOBEC3 is a physiologically functioning restriction factor to mouse gammaretroviruses.
Complement Receptor 3 Promotes Severe Ross River Virus-Induced Disease
Authors: Morrison Thomas E. , Simmons Jason D. , Heise Mark T.
Published: September 2008

Alphaviruses such as Ross River virus (RRV) and chikungunya virus are mosquito-transmitted viruses that cause explosive epidemics of debilitating arthritis and myositis affecting millions of humans worldwide. Previous studies using a mouse model of RRV-induced disease demonstrated that viral infection results in a severe inflammatory arthritis and myositis and that complement component 3 (C3) contributes to the destructive phase of the inflammatory disease but not the recruitment of cellular infiltrates to the sites of RRV-induced inflammation. Here, we demonstrate that mice deficient in complement receptor 3 (CR3) (CD11b−/−), a signaling receptor activated by multiple ligands including the C3 cleavage fragment iC3b, develop less-severe disease signs and decreased tissue destruction compared to RRV-infected wild-type mice. CR3 deficiency had no effect on viral replication, nor did it diminish the magnitude, kinetics, and composition of the cellular infiltrates at the sites of inflammation. However, the genetic absence of CR3 diminished the expression of specific proinflammatory and cytotoxic effectors, including S100A9/S100A8 and interleukin-6, within the inflamed tissues, suggesting that CR3-dependent signaling at the sites of inflammation contributes to tissue damage and severe disease.
With Minimal Systemic T-Cell Expansion, CD8+T Cells Mediate Protection of Rhesus Macaques Immunized with Attenuated Simian-Human Immunodeficiency Virus SHIV89.6 from Vaginal Challenge with Simian Immunodeficiency Virus
Authors: Genescà Meritxell , Skinner Pamela J. , Hong Jung Joo , Li Jun , Lu Ding , McChesney Michael B. , Miller Christopher J.
Published: September 2008

The presence, at the time of challenge, of antiviral effector T cells in the vaginal mucosa of female rhesus macaques immunized with live-attenuated simian-human immunodeficiency virus 89.6 (SHIV89.6) is associated with consistent and reproducible protection from pathogenic simian immunodeficiency virus (SIV) vaginal challenge (18). Here, we definitively demonstrate the protective role of the SIV-specific CD8+T-cell response in SHIV-immunized monkeys by CD8+lymphocyte depletion, an intervention that abrogated SHIV-mediated control of challenge virus replication and largely eliminated the SIV-specific T-cell responses in blood, lymph nodes, and genital mucosa. While in the T-cell-intact SHIV-immunized animals, polyfunctional and degranulating SIV-specific CD8+T cells were present in the genital tract and lymphoid tissues from the day of challenge until day 14 postchallenge, strikingly, expansion of SIV-specific CD8+T cells in the immunized monkeys was minimal and limited to the vagina. Thus, protection from uncontrolled SIV replication in animals immunized with attenuated SHIV89.6 is primarily mediated by CD8+T cells that do not undergo dramatic systemic expansion after SIV challenge. These findings demonstrate that despite, and perhaps because of, minimal systemic expansion of T cells at the time of challenge, a stable population of effector-cytotoxic CD8+T cells can provide significant protection from vaginal SIV challenge.
The consequences of fluid motion in volcanic conduits
Authors: Gilbert Jennie S. , Lane Stephen J.
Published: September 2008

When volcanoes are active, there are characteristic signs such as ground movement, sounds, heat and ejected material. Each of these signs is a result of, and hence an information source for, fluid motion in volcanic conduits. Here we briefly review some of the links between these signs and fluid flow processes and suggest future directions that should allow advancement of eruption forecasting as these links become understood more fully. Cross-fertilization between increasingly realistic numerical and experimental models, diverse geophysical data sources, and chemical and physical evidence in eruptive products can be achieved by simultaneously applying these approaches to well-studied volcanoes.
Cyclic activity at Soufrière Hills Volcano, Montserrat: degassing-induced pressurization and stick-slip extrusion
Authors: Lensky N. G. , Sparks R. S. J. , Navon O. , Lyakhovsky V.
Published: September 2008

The growth of lava domes is often associated with cyclic variations of ground deformation, seismicity and mass flux of gas and magma. We present a model of cyclic volcanic activity which is controlled by degassing of supersaturated magma, magma flow into the conduit, gas escape from the permeable magma, deformation of the conduit walls and the friction between the walls and the plug at the top of the conduit. When the difference between magma pressure and ambient pressure exceeds the static friction, motion begins, bubbles expand and overpressure relaxes. Bubble expansion builds permeability, allows gas escape and faster depressurization. Depressurization and crystallization of the magma build supersaturation and gas diffusion from melt to bubbles. Gas flux into bubbles and magma flux from the chamber act to increase pressure. The rate of extrusion is controlled by the gas pressure, driving the motion, and by the rate- and state-dependent friction along shear zones between the plug and the host rock. When the magma overpressure drops to the dynamic strength of the slip surfaces, the plug sticks and blocks the vent. As bubble volume is now constant, exsolution of gas from the supersaturated melt leads to pressurization and begins a new cycle.
Damping of pressure waves in visco-elastic, saturated bubbly magma
Authors: Kurzon I. , Lyakhovsky V. , Navon O. , Lensky N. G.
Published: September 2008

The attenuation of pressure waves in a saturated bubbly magma is examined in a model, coupling seismic wave-propagation with bubble growth dynamics. This model is solved analytically and numerically, including effects of diffusion of volatiles, visco-elasticity and bubble number density. We show that wave attenuation is controlled mainly by the
Peclet
and
Deborah
numbers. The
Peclet
number is a measure of the relative importance of advection to diffusion. The
Deborah
number is a visco-elastic measure, describing the importance of elasticity in comparison to viscous melt deformation. We solve numerically for wave attenuation for various magma properties corresponding to a wide range of
Peclet
and
Deborah
numbers. We show that the numerical solution can be approximated quite well for frequencies above 1 Hz, by an analytical end-member solution, obtained for high
Peclet
and low
Deborah
numbers. For lower frequencies, volatile transport should be accounted for, leading to higher attenuation with respect to the analytical solution. However, if the
Deborah
number is increased, either by longer relaxation time or by higher frequencies, then attenuation decreases with respect to the analytical solution. Therefore, visco-elasticity leads to a significant improvement of the resonating qualities of a magma-filled conduit and widens the depth and frequency ranges where pressure waves will propagate efficiently through the conduit.
Molecular profile of endothelial invasion of three-dimensional collagen matrices: insights into angiogenic sprout induction in wound healing
Authors: Su Shih-Chi , Mendoza E. Adriana , Kwak Hyeong-il , Bayless Kayla J.
Published: September 2008

Sprouting angiogenesis is a multistep process consisting of basement membrane degradation, endothelial cell (EC) activation, proliferation, invasion, lumen formation, and sprout stabilization. Such complexity is consistent with a requirement for orchestration of individual gene expression alongside multiple signaling pathways. To better understand the mechanisms that direct the transformation of adherent ECs on the surface of collagen matrices to develop multicellular invading sprouts, we analyzed differential gene expression with time using a defined in vitro model of EC invasion driven by the combination of sphingosine-1-phosphate, basic FGF, and VEGF. Gene expression changes were confirmed by real-time PCR and Western blot analyses. A cohort of cell adhesion molecule genes involved in adherens junction and cell-extracellular matrix (ECM) interactions were upregulated, whereas a set of genes associated with tight junctions were downregulated. Numerous genes encoding ECM proteins and proteases were induced, indicating that biosynthesis and remodeling of ECM is indispensable for sprouting angiogenesis. Knockdown of a highly upregulated gene, a disintegrin and metalloproteinase with thrombospondin-type repeats-1 (ADAMTS1), decreased invasion responses, confirming a role for ADAMTS1 in mediating EC invasion. Furthermore, differential expression of multiple members of the Wnt and Notch pathways was observed. Functional experiments indicated that inhibition and activation of the Notch signaling pathway stimulated and inhibited EC invasion responses, respectively. This study has enhanced the molecular road map of gene expression changes that occur during endothelial invasion and highlighted the utility of three-dimensional models to study EC morphogenesis.
Activation of Hsp90-eNOS and increased NO generation attenuate respiration of hypoxia-treated endothelial cells
Authors: Presley Tennille , Vedam Kaushik , Velayutham Murugesan , Zweier Jay L. , Ilangovan Govindasamy
Published: September 2008

Hypoxia induces various adoptive signaling in cells that can cause several physiological changes. In the present work, we have observed that exposure of bovine aortic endothelial cells (BAECs) to extreme hypoxia (1–5% O2) attenuates cellular respiration by a mechanism involving heat shock protein 90 (Hsp90) and endothelial nitric oxide (NO) synthase (eNOS), so that the cells are conditioned to consume less oxygen and survive in prolonged hypoxic conditions. BAECs, exposed to 1% O2, showed a reduced respiration compared with 21% O2-maintained cells. Western blot analysis showed an increase in the association of Hsp90-eNOS and enhanced NO generation on hypoxia exposure, whereas there was no significant accumulation of hypoxia-inducible factor-1α (HIF-1α). The addition of inhibitors of Hsp90, phosphatidylinositol 3-kinase, and NOS significantly alleviated this hypoxia-induced attenuation of respiration. Thus we conclude that hypoxia-induced excess NO and its derivatives such as ONOO− cause inhibition of the electron transport chain and attenuate O2 demand, leading to cell survival at extreme hypoxia. More importantly, such an attenuation is found to be independent of HIF-1α, which is otherwise thought to be the key regulator of respiration in hypoxia-exposed cells, through a nonphosphorylative glycolytic pathway. The present mechanistic insight will be helpful to understand the difference in the magnitude of endothelial dysfunction.
The effect of C1 inhibitor on intestinal ischemia and reperfusion injury
Authors: Lu Fengxin , Chauhan Anil K. , Fernandes Stacey M. , Walsh Meghan T. , Wagner Denisa D. , Davis Alvin E.
Published: September 2008

Complement activation and neutrophil stimulation are two major components in events leading to ischemia and reperfusion (IR) injury. C1 inhibitor (C1INH) inhibits activation of each of the three pathways of complement activation and of the contact system. It is also endowed with anti-inflammatory properties that are independent of protease inhibition. The goal of these studies was to investigate the role and mechanism of C1INH in alleviating IR-induced intestinal injury. C57BL/6, C1INH-deficient (C1INH−/−), bradykinin type 2 receptor-deficient (Bk2R−/−), and C3-deficient mice (C3−/−) were randomized into three groups: sham operated control, IR, and IR + C1INH-treated groups. Ischemia was generated by occlusion of the superior mesenteric artery followed by reperfusion. C1INH or reactive center-cleaved inactive C1INH (iC1INH) was injected intravenously before reperfusion. IR resulted in intestinal injury in C57BL/6, C1INH−/−, Bk2R−/−, and C3−/−mice with significantly increased neutrophil infiltration into intestinal tissue. In each mouse strain, C1INH treatment reduced intestinal tissue injury and attenuated leukocyte infiltration compared with the untreated IR group. C1INH inhibited leukocyte rolling in the mesenteric veins of both C57BL/6 and C3-deficient mice subjected to IR. C1INH treatment also improved the survival rate of C57BL/6 and C1INH−/−mice following IR. Similar findings were observed in the IR animals treated with iC1INH. These studies emphasize the therapeutic benefit of C1INH in preventing intestinal injury caused by IR. In addition to the protective activities mediated via inhibition of the complement system, these studies indicate that C1INH also plays a direct role in suppression of leukocyte transmigration into reperfused tissue.
Superoxide dismutase restores eNOS expression and function in resistance pulmonary arteries from neonatal lambs with persistent pulmonary hypertension
Authors: Farrow Kathryn N. , Lakshminrusimha Satyan , Reda William J. , Wedgwood Stephen , Czech Lyubov , Gugino Sylvia F. , Davis Jonathan M. , Russell James A. , Steinhorn Robin H.
Published: September 2008

Endothelial nitric oxide (NO) synthase (eNOS) expression and activity are decreased in fetal lambs with persistent pulmonary hypertension (PPHN). We sought to determine the impact of mechanical ventilation with O2 with or without inhaled NO (iNO) or recombinant human SOD (rhSOD) on eNOS in the ductal ligation model of PPHN. PPHN lambs and age-matched controls were ventilated with 100% O2 for 24 h alone or combined with 20 ppm iNO continuously or a single dose of rhSOD (5 mg/kg) given intratracheally at delivery. In 1-day spontaneously breathing lambs, eNOS expression in resistance pulmonary arteries increased relative to fetal levels. eNOS expression increased in control lambs ventilated with 100% O2, but not in PPHN lambs. Addition of iNO or rhSOD increased eNOS expression and decreased generation of reactive oxygen species (ROS) in PPHN lambs relative to those ventilated with 100% O2 alone. However, only rhSOD restored eNOS function, increased tetrahydrobiopterin (BH4), a critical cofactor for eNOS function, and restored GTP cyclohydrolase I expression in isolated vessels and lungs from PPHN lambs. These data suggest that ventilation of PPHN lambs with 100% O2 increases ROS production, blunts postnatal increases in eNOS expression, and decreases available BH4 in PPHN lambs. Although the addition of iNO or rhSOD diminished ROS production and increased eNOS expression, only rhSOD improved eNOS function and levels of available BH4. Thus therapies designed to decrease oxidative stress and restore eNOS coupling, such as rhSOD, may prove useful in the treatment of PPHN in newborn infants.
Observations on the physiological interactions between obesity and asthma
Authors: Nicolacakis Katina , Skowronski Mary E. , Coreno Albert J. , West Erin , Nader Nizar Z. , Smith Robert L. , McFadden E. R.
Published: September 2008

To explore whether asthma and obesity share overlapping pathogenic features, we examined the impact of each alone, and in combination, on multiple aspects of lung function. We reasoned that if they influenced the lungs through similar mechanisms, the individual physiological manifestations in the comorbid state should interact in a complex fashion. If not, then the abnormalities should simply add. We measured specific conductance, spirometry, lung volumes, and airway responsiveness to adrenergic and cholinergic agonists in 52 normal, 53 asthmatic, 52 obese, and 53 asthmatic and obese patients using standard techniques. Six-minute walks were performed in subsets from each group. Asthma significantly lowered specific conductance and the spirometric variables while increasing airway reactivity and residual volume. Obesity also reduced the spirometric variables as well as total lung capacity and functional residual capacity. Residual volume, specific conductance, and airway responsivity were unaltered. With comorbidity, the disease-specific derangements added algebraically. Features that existed in isolation appeared unchanged in the combination, whereas shared ones either added or subtracted depending on the individual directional changes. Synergistic interactions were not observed. Body mass index weakly correlated with spirometry and lung volumes in asthma, but not with specific conductance or bronchial reactivity. Exercise performance did not aid in differentiation. Our findings indicate asthma and obesity appear to influence the respiratory system through different processes.
Role of respiratory control mechanisms in the pathogenesis of obstructive sleep disorders
Authors: Younes Magdy
Published: September 2008

Obstructive sleep disorders develop when the normal reduction in pharyngeal dilator activity at sleep onset occurs in an individual whose pharynx requires a relatively high level of dilator activity to remain sufficiently open. They range from steady snoring, to slowly evolving hypopneas, to fast-recurring obstructive hypopneas and apneas. A fundamental observation is that the polysomnographic picture differs substantially among subjects with the same pharyngeal collapsibility, and even in the same subject at different times, indicating that the type and severity of the disorder is determined to a large extent by the individual's response to the obstruction. The present report reviews the various mechanisms involved in the response to sleep-induced obstructive events. When the obstructive event takes the form of mild-moderate flow limitation, compensation can take place through an increase in the fraction of time spent in inspiration (Ti/Ttot) without any increase in maximum flow (V̇MAX). With more severe obstructions, V̇MAXmust increase. Recent data indicate that the obstructed upper airway can reopen reflexly, without arousal, if chemical drive is allowed to reach a threshold (TER) but that this is often preempted by a low arousal threshold. The relation between TERand arousal threshold, as well as the lung-to-carotid circulation time and the rate of rise of chemical drive during the obstructive event, determine the magnitude of ventilatory overshoot at the end of an event and, by extension, whether initial obstructive events will be followed by stable breathing, slow evolving hypopneas with occasional arousals, or repetitive events.
Methylseleninic acid synergizes with tamoxifen to induce caspase-mediated apoptosis in breast cancer cells
Authors: Li Zengshan , Carrier Latonya , Rowan Brian G.
Published: September 2008

Tamoxifen has efficacy as a breast cancer therapy and chemoprevention agent. However, toxicity and resistance to tamoxifen limit its clinical application. There is an urgent need to develop compounds that may be combined with tamoxifen to improve efficacy and overcome toxicity and resistance. We showed previously that the organoselenium compound methylseleninic acid (MSA) increased the growth-inhibitory effect of tamoxifen and reversed tamoxifen resistance in breast cancer cells. In this study, we examined the mechanism for induction of apoptosis by MSA combined with tamoxifen in tamoxifen-sensitive and tamoxifen-resistant breast cancer cells. 4-hydroxytamoxifen (TAM; 10−7 mol/L) alone resulted in cell cycle arrest but no apoptosis, whereas MSA alone (10 μmol/L) induced apoptosis in tamoxifen-sensitive cells. Combination of MSA with TAM resulted in a synergistic apoptosis in both tamoxifen-sensitive and tamoxifen-resistant breast cancer cells compared with either agent alone. MSA and MSA combined with TAM induced apoptosis through the intrinsic, mitochondrial apoptotic pathway. MSA induced a sequential activation of caspase-9 and then caspase-8. These results indicate that the growth inhibition synergy and reversal of tamoxifen resistance by combination of selenium with tamoxifen occurs via a tamoxifen-induced cell cycle arrest, allowing more cells to enter the intrinsic apoptotic pathway elicited by selenium. [Mol Cancer Ther 2008;7(9):3056–63]
Curcumin inhibits Akt/mammalian target of rapamycin signaling through protein phosphatase-dependent mechanism
Authors: Yu Siwang , Shen Guoxiang , Khor Tin Oo , Kim Jung-Hwan , Kong Ah-Ng Tony
Published: September 2008

Akt/mammalian target of rapamycin (mTOR) signaling plays an important role in tumorigenesis and is dysregulated in many tumors, especially metastatic prostate cancers. Curcumin has been shown to effectively prevent or inhibit prostate cancer in vivo and inhibit Akt/mTOR signaling in vitro, but the mechanism(s) remains unclear. Here, we show that curcumin concentration- and time-dependently inhibited the phosphorylation of Akt, mTOR, and their downstream substrates in human prostate cancer PC-3 cells, and this inhibitory effect acts downstream of phosphatidylinositol 3-kinase and phosphatidylinositol-dependent kinase 1. Overexpression of constitutively activated Akt or disruption of TSC1-TSC2 complex by small interfering RNA or gene knockout only partially restored curcumin-mediated inhibition of mTOR and downstream signaling, indicating that they are not the primary effectors of curcumin-mediated inhibition of Akt/mTOR signaling. Curcumin also activated 5′-AMP-activated protein kinase and mitogen-activated protein kinases; however, inhibition of these kinases failed to rescue the inhibition by curcumin. Finally, it was shown that the inhibition of Akt/mTOR signaling by curcumin is resulted from calyculin A-sensitive protein phosphatase-dependent dephosphorylation. Our study reveals the profound effects of curcumin on the Akt/mTOR signaling network in PC-3 cells and provides new mechanisms for the anticancer effects of curcumin. [Mol Cancer Ther 2008;7(9):2609–20]
N-&-N, a new class of cell death-inducing kinase inhibitors derived from the purine roscovitine
Authors: Bettayeb Karima , Sallam Hatem , Ferandin Yoan , Popowycz Florence , Fournet Guy , Hassan Moustapha , Echalier Aude , Bernard Philippe , Endicott Jane , Joseph Benoît , Meijer Laurent
Published: September 2008

Cyclin-dependent kinases (CDKs) and their regulators show frequent abnormalities in tumors. Ten low molecular weight pharmacologic inhibitors of CDKs are currently in clinical trials against various cancers, including the 2,6,9-trisubstituted purine (R)-roscovitine (CYC202/Seliciclib). We here report the characterization of N-&-N1, a bioisoster of roscovitine displaying improved antitumoral properties. N-&-N1 shows exquisite selectivity for CDKs, with 2- to 3-fold enhanced potency compared with (R)-roscovitine. Inhibition of retinoblastoma protein phosphorylation and RNA polymerase II Ser2 phosphorylation in neuroblastoma SH-SY5Y cells exposed to N-&-N1 indicates that N-&-N1 is able to inhibit CDKs in a cellular context. N-&-N1 also down-regulates the expression of RNA polymerase. Cocrystal structures of N-&-N1 and (R)-roscovitine in complex with CDK2/cyclin A reveal that both inhibitors adopt similar binding modes. A competitive assay shows that, compared with (R)-roscovitine, N-&-N1 has reduced affinity for Erk2 and pyridoxal kinase. N-&-N1 triggers cell death in a panel of diverse cell lines. Cell death is accompanied by events characteristic of apoptosis: cytochrome c release, activation of effector caspases, and poly(ADP-ribose) polymerase cleavage. Induction of p53 and p21CIP1 and down-regulation of the Mcl-1 antiapoptotic factor were also observed. Studies in mice show that N-&-N1 has pharmacokinetics properties similar to those of (R)-roscovitine. Altogether, these results show that analogues of (R)-roscovitine can be designed with improved antitumor potential. [Mol Cancer Ther 2008;7(9):2713–24]
hKSR-2, a vitamin D–regulated gene, inhibits apoptosis in arabinocytosine-treated HL60 leukemia cells
Authors: Wang Xuening , Patel Rahul , Studzinski George P.
Published: September 2008

Ras signaling can be modulated by the scaffolding activity of kinase suppressor of Ras-1 (KSR-1) and by the hKSR-2 protein, resulting in diverse phenotypic outcomes. The mitogen-activated protein kinase cascade downstream from Ras and KSRs includes Raf-1 and extracellular signal-regulated kinase 1/2 kinases, known to enhance survival potential of a range of cell types. Because the molecular events that increase survival of HL60 cells induced to differentiate toward monocytic phenotype by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] are not known, we investigated if KSR proteins provide a survival function in these cells. We found that whereas kinase suppressor of Ras-1 had no detectable effect on cell survival in the system studied here, 1,25-(OH)2D3-induced up-regulation of hKSR-2 enhanced the resistance of HL60 cells to arabinocytosine. Knockdown of hKSR-2 by either small interfering RNA or antisense oligonucleotides increased arabinocytosine-induced apoptosis, which was accompanied by reduced Bcl-2/Bax and Bcl-2/Bad ratios, and increased caspase-3 activating cleavage. In contrast, up-regulation of Mcl-1 was not abrogated by anti-sense (AS) AS-hKSR-2, pointing to a specific role of Bcl-2 in control of 1,25-(OH)2D3-induced increased cell survival. These findings are consistent with the previously shown lack of fully differentiated monocytic cells in HL60 cultures exposed to 1,25-(OH)2D3 in which hKSR-2 was knocked down, suggesting that optimal differentiation of these cells requires enhanced antiapoptotic mechanisms provided, at least in part, by hKSR-2. Collectively, these results suggest that hKSR-2 may offer a new target for novel therapies of acute myelogenous leukemia. [Mol Cancer Ther 2008;7(9):2798–806]
Pharmacokinetic-directed dosing of vandetanib and docetaxel in a mouse model of human squamous cell carcinoma
Authors: Bradshaw-Pierce Erica L. , Steinhauer Courtney A. , Raben David , Gustafson Daniel L.
Published: September 2008

Docetaxel, usually administered according to maximum tolerated dose (MTD), can inhibit endothelial cell proliferation at low nanomolar concentrations. Docetaxel may exert antiangiogenic effects if dosed so plasma levels are maintained at low nanomolar concentrations over a prolonged time. We evaluated metronomic and MTD-based dosing of docetaxel with and without vandetanib, a vascular endothelial growth factor receptor-2 and epidermal growth factor receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity, in a head and neck xenograft model. A murine physiologically based pharmacokinetic model was modified to predict docetaxel distribution following i.p. administration to design dosing regimens that target prespecified plasma concentrations, for antiendothelial effects (metronomic), or exposure, to mimic 30 mg/m2 (weekly/MTD) docetaxel in humans. Animals were treated for 28 days with 1 mg/kg/d (DTX1) or 6 mg/kg q4d (DTX6) docetaxel with or without vandetanib (15 mg/kg/d p.o.) in mice bearing UMSCC2 tumor xenografts. The DTX1 dosing scheme was adjusted to treatment for 10 days followed by 9 days off due to severe gastrointestinal toxicity. All treatment groups significantly reduced tumor volume, tumor proliferation (Ki-67), and tumor endothelial cell proliferation (Ki-67/von Willebrand factor) compared with control. Addition of vandetanib to docetaxel treatment significantly enhanced tumor growth inhibition over single-agent therapy. A positive correlation of tumor endothelial cell proliferation with tumor growth rates demonstrates vandetanib and docetaxel antiangiogenic effects. Due to the morbidity observed with DTX1 treatment, it is difficult to clearly ascertain if metronomic schedules will be effective for treatment. Docetaxel with vandetanib is effective in treating UMSCC2 xenografts at concentrations relevant to exposures in humans. [Mol Cancer Ther 2008;7(9):3006–17]