bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical Study of Vibration Isolation Between a Pair of Flexible Structures
Authors: Zheng G. T. , Tu Y. Q.
Published: February 2009

The problem of flexible structure vibration isolation on a flexible foundation is analytically investigated by simplifying the vibration isolation as single axis isolation, which can be realized by a proper design, and the problem of the whole spacecraft vibration is taken as an example for the application as both the spacecraft (isolated structure) and the launch vehicle (foundation) are flexible structures. A numerical example of the whole spacecraft vibration isolation is also provided for further explaining those conclusions derived from the analytical studies. It is found from the study that the isolator’s damping is important for attenuating the vibration and that weakening the isolator’s stiffness has the same effect as increasing its damping. However, a weaker stiffness means a weaker coupling among the structures and may magnify the vibration at some resonant frequencies, which are close to those of individual structures. The coupling effect of the structure’s flexibility on the isolation may be significant in some cases and a coupling analysis is essential for ensuring the isolation performance. Because of the importance of the isolator’s damping in reducing the vibration transmissibility and the vibration of the coupled structure, it is more appropriate to describe the vibration isolation of the flexible structure as vibration attenuation.
Ground-Based Vibration Response of a Spinning, Cyclic, Symmetric Rotor With Gyroscopic and Centrifugal Softening Effects
Authors: Kim Hyunchul , Shen I. Y.
Published: February 2009

This paper is to study ground-based vibration response of a spinning, cyclic, symmetric rotor through a theoretical analysis and an experimental study. The theoretical analysis consists of three steps. The first step is to analyze the vibration characteristics of a stationary, cyclic, symmetric rotor with N identical substructures. For each vibration mode, we identify a phase index n and derive a Fourier expansion of the mode shape in terms of the phase index n. The second step is to predict the rotor-based vibration response of the spinning, cyclic, symmetric rotor based on the Fourier expansion of the mode shapes and the phase indices. The rotor-based formulation includes gyroscopic and centrifugal softening terms. Moreover, rotor-based response of repeated modes and distinct modes is obtained analytically. The third step is to transform the rotor-based response to ground-based response using the Fourier expansion of the stationary mode shapes. The theoretical analysis leads to the following conclusions. First, gyroscopic effects have no significant effects on distinct modes. Second, the presence of gyroscopic and centrifugal softening effects causes the repeated modes to split into two modes with distinct frequencies ω1 and ω2 in the rotor-based coordinates. Third, the transformation to ground-based observers leads to primary and secondary frequency components. In general, the ground-based response presents frequency branches in the Campbell diagram at ω1±kω3 and ω2±kω3, where k is phase index n plus an integer multiple of cyclic symmetry N. When the gyroscopic effect is significantly greater than the centrifugal softening effect, two of the four frequency branches vanish. The remaining frequency branches take the form of either ω1+kω3 and ω2−kω3 or ω1−kω3 and ω2+kω3. To verify these predictions, we also conduct a modal testing on a spinning disk carrying four pairs of brackets evenly spaced in the circumferential direction with ground-based excitations and responses. The disk-bracket system is mounted on a high-speed, air-bearing spindle. An automatic hammer excites the spinning disk-bracket system and a laser Doppler vibrometer measures its vibration response. A spectrum analyzer processes the hammer excitation force and the vibrometer measurements to obtain waterfall plots at various spin speeds. The measured primary and secondary frequency branches from the waterfall plots agree well with those predicted analytically.
Numerical Simulation of Aero-Engine Lubrication System
Authors: Lu Yaguo , Liu Zhenxia , Huang Shengqin , Xu Tao
Published: February 2009

A software, general analysis software of aero-engine lubrication system (GASLS), for simulating aero-engine lubrication system is presented. The software is capable of analyzing the flow, pressure, and temperature distribution in the lubrication system. The network theory and mathematical model of flow resistance for elements that include pipes, elbows, thick orifice, reductions, expansions, and nozzles are presented first. Second, the special element and combined element are introduced for treating the bearing chamber, heat exchanger, and gearbox and simplifying the calculation network, respectively. Lastly, a case study for an aero-engine lubrication system is illustrated. The distribution of oil flow, pressure, and temperature is calculated, and the oil flow results in different branches of lubrication system are compared with the experimental data. The comparison indicts that computational results agree well with the measured data. The software may be helpful in designing and analyzing aero-engine lubrication system.
Fast Epitaxial High Temperature Brazing of Single Crystalline Nickel Based Superalloys
Authors: Laux Britta , Piegert Sebastian , Rösler Joachim
Published: February 2009

A new high temperature brazing technology for the repair of turbine components made of single crystalline nickel based superalloys has been developed. It allows the repair of single crystalline parts by producing an epitaxially grown braze gap within very short times. In contrast to commonly used brazing technologies, the process is not diffusion based but works with consolute systems, particularly nickel-manganese alloys. Brazing experiments with 300 μm wide parallel braze gaps, as well as V-shaped gaps with a maximum width of 250 μm, were conducted. Furthermore, thermodynamic simulations, with the help of THERMOCALC software, Version TCR, were carried out to identify compositions with a suitable melting behavior and phase formation. With the new alloys complete, epitaxial bridging of both gap shapes has been achieved within brazing times as short as 10 min.
Analysis of NOx Formation in a Hydrogen-Fueled Gas Turbine Engine
Authors: Therkelsen Peter , Werts Tavis , McDonell Vincent , Samuelsen Scott
Published: February 2009

A commercially available natural gas fueled gas turbine engine was operated on hydrogen. Three sets of fuel injectors were developed to facilitate stable operation while generating differing levels of fuel∕air premixing. One set was designed to produce near uniform mixing while the others have differing degrees of nonuniformity. The emission performance of the engine over its full range of loads is characterized for each of the injector sets. In addition, the performance is also assessed for the set with near uniform mixing as operated on natural gas. The results show that improved mixing and lower equivalence ratio decrease NO emission levels as expected. However, even with nearly perfect premixing, it is found that the engine, when operated on hydrogen, produces a higher amount of NO than when operated with natural gas. Much of this attributed to the higher equivalence ratios that the engine operates on when firing hydrogen. However, even the lowest equivalence ratios run at low power conditions, higher NO was observed. Analysis of the potential NO formation effects of residence time, kinetic pathways of NO production via NNH, and the kinetics of the dilute combustion strategy used are evaluated. While no one mechanism appears to explain the reasons for the higher NO, it is concluded that each may be contributing to the higher NO emissions observed with hydrogen. In the present configuration with the commercial control system operating normally, it is evident that system level effects are also contributing to the observed NO emission differences between hydrogen and natural gas.
Experimental Study on Effects of Slot Hot Blowing on Secondary Water Droplet Size and Water Film Thickness
Authors: Li Chunguo , Wang Xinjun , Cheng Daijing , Sun Bi
Published: February 2009

The effects of the slot hot blowing of the hollow stator blades on the size of secondary water droplets and the thickness of the water film were experimentally investigated in this paper. The experiment was carried out on the turbine blade cascades in a wet air tunnel with an inlet air wetness fraction of 7.9%, an outlet air velocity of 170 m/s, a slot width of 1.0 mm, and a slot angle of 45 deg to blade surface. The Malvern droplet and particle size analyzer was utilized to measure the secondary water droplet size and distribution downstream of the hollow stator blades in the experimental tests. The experimental results show that the maximum diameter and Sauter mean diameter of the secondary water droplets were reduced greatly, and the water droplet size distribution became narrower. The larger blowing pressure difference resulted in the smaller secondary water droplets and the narrower water droplet size distributions. In addition, the efficiency of water separation from the hollow stator blade surfaces was higher for slot on the suction side than that of the pressure side case. Another simplified experimental test was also carried out on the flat plate to investigate the effect of slot hot blowing on the thickness of the water film downstream of the slot. The conductivity probes were used to measure the thickness of the water film downstream and upstream of the blowing slot. The results show that the slot hot blowing reduced the thickness of the water film downstream of the slot, which was affected by the blowing pressure difference and temperature difference between the hot blowing air and the main airflow. In conclusion, the slot hot blowing of the hollow stator blades has reduced the size of the secondary water droplets and secondarily has evaporated a little water film on the blade surfaces. Both effects are beneficial to reduce the erosion damage to the rotor blades.
Extending the Lean Limit of Natural-Gas Engines
Authors: Evans R. L.
Published: February 2009

Two different methods to improve the thermal efficiency and reduce the emissions from lean-burn natural-gas fueled engines have been developed and are described in this paper. One method used a “squish-jet” combustion chamber designed specifically to enhance turbulence generation, while the second method provided a partially stratified-charge mixture near the spark plug in order to enhance the ignition of lean mixtures of natural gas and air. The squish-jet combustion chamber was found to reduce brake specific fuel consumption by up to 4.8% in a Ricardo Hydra engine, while the NOx efficiency trade-off was greatly improved in a Cummins L-10 engine. The partially stratified-charge combustion system extended the lean limit of operation in the Ricardo Hydra by some 10%, resulting in a 64% reduction in NOx emissions at the lean limit of operation. Both techniques were also shown to be effective in increasing the stability of combustion, thereby reducing cyclic variations in cylinder pressure.
Isotopic Evidence for an Aerobic Nitrogen Cycle in the Latest Archean
Authors: Garvin Jessica , Buick Roger , Anbar Ariel D. , Arnold Gail L. , Kaufman Alan J.
Published: February 2009

The nitrogen cycle provides essential nutrients to the biosphere, but its antiquity in modern form is unclear. In a drill core though homogeneous organic-rich shale in the 2.5-billion-year-old Mount McRae Shale, Australia, nitrogen isotope values vary from +1.0 to +7.5 per mil (‰) and back to +2.5‰ over ∼30 meters. These changes evidently record a transient departure from a largely anaerobic to an aerobic nitrogen cycle complete with nitrification and denitrification. Complementary molybdenum abundance and sulfur isotopic values suggest that nitrification occurred in response to a small increase in surface-ocean oxygenation. These data imply that nitrifying and denitrifying microbes had already evolved by the late Archean and were present before oxygen first began to accumulate in the atmosphere.
Stress-Inducible Regulation of Heat Shock Factor 1 by the Deacetylase SIRT1
Authors: Westerheide Sandy D. , Anckar Julius , Stevens Stanley M. , Sistonen Lea , Morimoto Richard I.
Published: February 2009

Heat shock factor 1 (HSF1) is essential for protecting cells from protein-damaging stress associated with misfolded proteins and regulates the insulin-signaling pathway and aging. Here, we show that human HSF1 is inducibly acetylated at a critical residue that negatively regulates DNA binding activity. Activation of the deacetylase and longevity factor SIRT1 prolonged HSF1 binding to the heat shock promoter Hsp70 by maintaining HSF1 in a deacetylated, DNA–binding competent state. Conversely, down-regulation of SIRT1 accelerated the attenuation of the heat shock response (HSR) and release of HSF1 from its cognate promoter elements. These results provide a mechanistic basis for the requirement of HSF1 in the regulation of life span and establish a role for SIRT1 in protein homeostasis and the HSR.
A Foundation, But Can We Use It?
Authors: Wertsch James V.
Published: February 2009

The Future of Education
. Reimagining Our Schools from the Ground Up.
By Kieran Egan
. Yale University Press, New Haven, CT, 2008. 203 pp. $30. ISBN 9780300110463.

Egan argues that the three principal goals of current education--academic, social, and developmental growth--are fundamentally incompatible and therefore "destined to defeat our best efforts." He proposes a complete overhaul of teaching and the curriculum and presents a speculative account of the next half-century to describe how we might achieve that.
A Self-Regulatory System of Interlinked Signaling Feedback Loops Controls Mouse Limb Patterning
Authors: Bénazet Jean-Denis , Bischofberger Mirko , Tiecke Eva , Gonçalves Alexandre , Martin James F. , Zuniga Aimée , Naef Felix , Zeller Rolf
Published: February 2009

Embryogenesis depends on self-regulatory interactions between spatially separated signaling centers, but few of these are well understood. Limb development is regulated by epithelial-mesenchymal (e-m) feedback loops between sonic hedgehog (SHH) and fibroblast growth factor (FGF) signaling involving the bone morphogenetic protein (BMP) antagonist Gremlin1 (GREM1). By combining mouse molecular genetics with mathematical modeling, we showed that BMP4 first initiates and SHH then propagates e-m feedback signaling through differential transcriptional regulation of
Grem1
to control digit specification. This switch occurs by linking a fast BMP4/GREM1 module to the slower SHH/GREM1/FGF e-m feedback loop. This self-regulatory signaling network results in robust regulation of distal limb development that is able to compensate for variations by interconnectivity among the three signaling pathways.
Development of an Immunochromatographic Test for Rapid Serodiagnosis of Human Pythiosis
Authors: Krajaejun Theerapong , Imkhieo Srisurat , Intaramat Akarin , Ratanabanangkoon Kavi
Published: February 2009

Human pythiosis is an emerging and life-threatening infectious disease caused by the fungus-like organism
Pythium insidiosum
. High rates of morbidity and mortality for patients with pythiosis are exacerbated by the lack of early diagnosis and an effective treatment. Here, we developed and evaluated an immunochromatographic test (ICT) for the diagnosis of human pythiosis, in comparison to a standard serological test of immunodiffusion (ID). Culture filtrate antigen of
P. insidiosum
was used to detect human anti-
P. insidiosum
antibody. Sheep anti-human immunoglobulin G-colloidal gold conjugate was used to generate an ICT signal. Thirty-three sera from patients with vascular (
n
= 27), ocular (
n
= 4), and cutaneous (
n
= 2) pythiosis and 181 control sera from healthy blood donors (
n
= 100), as well as patients with a variety of infectious (
n
= 56) and noninfectious (
n
= 25) diseases, were included in the test evaluation. The turnaround time for generating a result by the ICT was less than 30 min, while that for ID was ∼24 h. Based on the results for all sera of pythiosis patients and the control groups, the ICT showed 88% sensitivity and 100% specificity and ID showed 61% sensitivity and 100% specificity. By both tests, false-negative results for sera from all ocular pythiosis patients were obtained. In addition, the ID test yielded false-negative results for sera from eight patients with vascular pythiosis and one patient with cutaneous pythiosis. It was concluded that the ICT is a rapid, user-friendly, and reliable serological test for the early diagnosis of vascular and cutaneous pythiosis.
Frequency of Missed Cases of Probable Acute West Nile Virus (WNV) Infection when Testing for WNV RNA Alone or WNV Immunoglobulin M Alone
Authors: Prince Harry E. , Calma Jan , Pham Tiffany , Seaton Brent L.
Published: February 2009

To estimate the frequency of missed cases of acute West Nile virus (WNV) infection if only WNV RNA or immunoglobulin M (IgM) testing is requested, we measured IgM in specimens negative for RNA and vice versa. Whereas 6 (5.5%) of 110 RNA-negative sera were IgM positive, only 3 (1.0%) of 299 IgM-negative sera were RNA positive (
P
< 0.05). Similarly, 11 (7.8%) of 141 RNA-negative cerebrospinal fluid specimens (CSF) were IgM positive, but 0 (0%) of 118 IgM-negative CSF were RNA positive (
P
< 0.05). WNV infections may be missed if only RNA or IgM testing is requested, with a higher frequency of missed cases if only RNA testing is requested.
Enhanced Antibody Responses Elicited by a CpG Adjuvant Do Not Improve the Protective Effect of an Aldrithiol-2-Inactivated Simian Immunodeficiency Virus Therapeutic AIDS Vaccine
Authors: Wang Yichuan , Blozis Shelley A. , Lederman Michael , Krieg Arthur , Landay Alan , Miller Christopher J.
Published: February 2009

The potential benefit of using unmethylated CpG oligoribodeoxynucleotides (ODN) as an adjuvant in a therapeutic simian immunodeficiency virus (SIV) vaccine consisting of AT2-inactivated SIVmac239 was evaluated in SIV-infected rhesus macaques receiving antiretroviral therapy (ART). We hypothesized that using CpG ODN as an adjuvant in therapeutic vaccination would enhance SIV-specific immune responses and suppress SIV replication after ART was stopped. To test our hypothesis, we immunized chronically SIV-infected rhesus macaques receiving ART with one of the following therapeutic vaccines: (i) AT2-inactivated SIVmac239, (ii) CpG10103 plus AT2-inactivated SIVmac239, (iii) CpG10103, and (iv) saline. While immunization with CpG plus AT2-SIVmac239 significantly increased SIV-specific immunoglobulin G (IgG) antibody titers, the mean plasma viral RNA (vRNA) level in these animals after ART did not differ from those of saline-treated animals. The AT2-inactivated SIVmac239-immunized animal group had a significantly higher mean SIV-specific gamma interferon T-cell response after three immunizations and lower plasma vRNA levels for 6 weeks after ART was withdrawn compared to the saline-treated animal group. Compared to the saline control group, the animal group treated with CpG alone had a significantly higher mean SIV-specific lymphocyte proliferation index and a higher rate of plasma vRNA rebound after ART. These results demonstrate that while the use of CpG as an adjuvant enhances SIV-specific antibody responses, this does not improve the control of SIV replication after ART is stopped. The lack of benefit may be related to the high levels of SIV-specific lymphocyte proliferation in the CpG adjuvant group.
A New Flavivirus and a New Vector: Characterization of a Novel Flavivirus Isolated from
Uranotaenia
Mosquitoes from a Tropical Rain Forest
Authors: Junglen Sandra , Kopp Anne , Kurth Andreas , Pauli Georg , Ellerbrok Heinz , Leendertz Fabian H.
Published: February 2009

A novel flavivirus was isolated from
Uranotaenia mashonaensis
, a mosquito genus not previously known to harbor flaviviruses. Mosquitoes were caught in the primary rain forest of the Taï National Park, Côte d'Ivoire. The novel virus, termed nounané virus (NOUV), seemed to grow only on C6/36 insect cells and not on vertebrate cells. Typical enveloped flavivirus-like particles of 60 to 65 nm in diameter were detected by electron microscopy in the cell culture supernatant of infected cells. The full genome was sequenced, and potential cleavage and glycosylation sites and cysteine residues were identified, suggesting that the processing of the NOUV polyprotein is similar to that of other flaviviruses. Phylogenetic analyses of the whole polyprotein and the NS3 protein showed that the virus forms a distinct cluster within the clade of mosquito-borne flaviviruses. Only a distant relationship to other known flaviviruses was found, indicating that NOUV is a novel lineage within the
Flaviviridae
.
Persistent West Nile Virus Associated with a Neurological Sequela in Hamsters Identified by Motor Unit Number Estimation
Authors: Siddharthan Venkatraman , Wang Hong , Motter Neil E. , Hall Jeffery O. , Skinner Robert D. , Skirpstunas Ramona T. , Morrey John D.
Published: February 2009

To investigate the hypothesis that neurological sequelae are associated with persistent West Nile virus (WNV) and neuropathology, we developed an electrophysiological motor unit number estimation (MUNE) assay to measure the health of motor neurons temporally in hamsters. The MUNE assay was successful in identifying chronic neuropathology in the spinal cords of infected hamsters. MUNE was suppressed at days 9 to 92 in hamsters injected subcutaneously with WNV, thereby establishing that a long-term neurological sequela does occur in the hamster model. MUNE suppression at day 10 correlated with the loss of neuronal function as indicated by reduced choline acetyltransferase staining (
R
2
= 0.91). Between days 10 and 26, some α-motor neurons had died, but further neuronal death was not detected beyond day 26. MUNE correlated with disease phenotype, because the lowest MUNE values were detected in paralyzed limbs. Persistent WNV RNA and foci of WNV envelope-positive cells were identified in the central nervous systems of all hamsters tested from 28 to 86 days. WNV-positive staining colocalized with the neuropathology, which suggested that persistent WNV or its products contributed to neuropathogenesis. These results established that persistent WNV product or its proteins cause dysfunction, that WNV is associated with chronic neuropathological lesions, and that this neurological sequela is effectively detected by MUNE. Inasmuch as WNV-infected humans can also experience a poliomyelitis-like disease where motor neurons are damaged, MUNE may also be a sensitive clinical or therapeutic marker for those patients.
Role of Defective Oct-2 and OCA-B Expression in Immunoglobulin Production and Kaposi's Sarcoma-Associated Herpesvirus Lytic Reactivation in Primary Effusion Lymphoma
Authors: Di Bartolo Daniel L. , Hyjek Elizabeth , Keller Shannon , Guasparri Ilaria , Deng Hongyu , Sun Ren , Chadburn Amy , Knowles Daniel M. , Cesarman Ethel
Published: February 2009

Primary effusion lymphoma (PEL) is a distinct type of B-cell non-Hodgkin lymphoma characterized by the presence of Kaposi's sarcoma-associated herpesvirus (KSHV/human herpesvirus 8). Despite having a genotype and gene expression signature of highly differentiated B cells, PEL does not usually express surface or cytoplasmic immunoglobulin (Ig). We show the lack of Oct-2 and OCA-B transcription factors to be responsible, at least in part, for this defect in Ig production. Like Ig genes, ORF50, the key regulator of the switch from latency to lytic reactivation, contains an octamer motif within its promoter. We therefore examined the impact of Oct-2 and OCA-B on ORF50 activation. The binding of Oct-1 to the ORF50 promoter has been shown to significantly enhance ORF50 transactivation. We found that Oct-2, on the other hand, inhibited ORF50 expression and consequently lytic reactivation by competing with Oct-1 for the octamer motif in the ORF50 promoter. Our data suggest that Oct-2 downregulation in infected cells would be favorable to KSHV in allowing for efficient viral reactivation.
Relaxed Selection and the Evolution of RNA Virus Mucin-Like Pathogenicity Factors
Authors: Wertheim Joel O. , Worobey Michael
Published: February 2009

Mucin-like regions contribute to pathogenicity in a variety of negative-stranded RNA viruses. These regions are characterized by a preponderance of O-linked glycosylation. They evolve exceptionally rapidly yet maintain their function as pathogenicity factors. Two hypotheses have been proposed to explain this evolutionary conundrum of phenotypic stability in the face of extreme genetic divergence: strong positive selection and relaxation of purifying selection. We determined the strength and direction of selection codon by codon across genes containing these regions and found that purifying selection is relaxed over the mucin-like regions relative to the genes in which they are found. This suggests that so long as these regions maintain sufficient O-linked glycosylation, they are free to evolve rapidly without loss of function as pathogenicity factors.
Isolation and Genetic Characterization of H5N2 Influenza Viruses from Pigs in Korea
Authors: Lee Jun Han , Pascua Philippe Noriel Q. , Song Min-Suk , Baek Yun Hee , Kim Chul-Joong , Choi Hwan-Woon , Sung Moon-Hee , Webby Richard J. , Webster Robert G. , Poo Haryoung , Choi Young Ki
Published: February 2009

Due to dual susceptibility to both human and avian influenza A viruses, pigs are believed to be effective intermediate hosts for the spread and production of new viruses with pandemic potential. In early 2008, two swine H5N2 viruses were isolated from our routine swine surveillance in Korea. The sequencing and phylogenetic analysis of surface proteins revealed that the Sw/Korea/C12/08 and Sw/Korea/C13/08 viruses were derived from avian influenza viruses of the Eurasian lineage. However, although the Sw/Korea/C12/08 isolate is an entirely avian-like virus, the Sw/Korea/C13/08 isolate is an avian-swine-like reassortant with the PB2, PA, NP, and M genes coming from a 2006 Korean swine H3N1-like virus. The molecular characterization of the two viruses indicated an absence of significant mutations that could be associated with virulence or binding affinity. However, animal experiments showed that the reassortant Sw/Korea/C13/08 virus was more adapted and was more readily transmitted than the purely avian-like virus in a swine experimental model but not in ferrets. Furthermore, seroprevalence in swine sera from 2006 to 2008 suggested that avian H5 viruses have been infecting swine since 2006. Although there are no known potential clinical implications of the avian-swine reassortant virus for pathogenicity in pigs or other species, including humans, at present, the efficient transmissibility of the swine-adapted H5N2 virus could facilitate virus spread and could be a potential model for pandemic, highly pathogenic avian influenza (e.g., H5N1 and H7N7) virus outbreaks or a pandemic strain itself.
Intersubunit Interactions Modulate pH-Induced Activation of Membrane Fusion by the Junín Virus Envelope Glycoprotein GPC
Authors: York Joanne , Nunberg Jack H.
Published: February 2009

The mature arenavirus envelope glycoprotein GPC is a tripartite complex comprising a stable signal peptide (SSP) in addition to the receptor-binding (G1) and transmembrane fusion (G2) subunits. We have shown previously that SSP is a key element in GPC-mediated membrane fusion, and that GPC sensitivity to acidic pH is modulated in part through the lysine residue at position 33 in the ectodomain loop of SSP (J. York and J. H. Nunberg, J. Virol. 80:7775-7780, 2006). A glutamine substitution at this position stabilizes the native GPC complex and thereby prevents the induction of pH-dependent membrane fusion. In efforts to identify the intersubunit interactions of K33, we performed alanine-scanning mutagenesis at charged residues in the membrane-proximal ectodomain of G2 and determined the ability of these mutations to rescue the fusion deficiency in K33Q GPC. Four second-site mutations that specifically complement K33Q were identified (D400A, E410A, R414A, and K417A). Moreover, complementation was also observed at three hydrophobic positions in the membrane-spanning domain of G2 (F427, W428, and F438). Interestingly, all of the complementing mutations restored wild-type pH sensitivity to the K33Q mutant, while none themselves affected the pH of membrane fusion. Our studies demonstrate a specific interaction between SSP and G2 that is involved in priming the native GPC complex for pH-induced membrane fusion. Importantly, this pH-dependent interaction has been shown to be vulnerable to small-molecule compounds that stabilize the native complex and prevent the activation of membrane fusion. A detailed mechanistic understanding of the control of GPC-mediated membrane fusion will be important in guiding the development of effective therapeutics against arenaviral hemorrhagic fever.
Foreign Glycoproteins Can Be Actively Recruited to Virus Assembly Sites during Pseudotyping
Authors: Jorgenson Rebecca L. , Vogt Volker M. , Johnson Marc C.
Published: February 2009

Retroviruses like human immunodeficiency virus type 1 (HIV-1), as well as many other enveloped viruses, can efficiently produce infectious virus in the absence of their own surface glycoprotein if a suitable glycoprotein from a foreign virus is expressed in the same cell. This process of complementation, known as pseudotyping, often can occur even when the glycoprotein is from an unrelated virus. Although pseudotyping is widely used for engineering chimeric viruses, it has remained unknown whether a virus can actively recruit foreign glycoproteins to budding sites or, alternatively, if a virus obtains the glycoproteins through a passive mechanism. We have studied the specificity of glycoprotein recruitment by immunogold labeling viral glycoproteins and imaging their distribution on the host plasma membrane using scanning electron microscopy. Expressed alone, all tested viral glycoproteins were relatively randomly distributed on the plasma membrane. However, in the presence of budding HIV-1 or Rous sarcoma virus (RSV) particles, some glycoproteins, such as those encoded by murine leukemia virus and vesicular stomatitis virus, were dramatically redistributed to viral budding sites. In contrast, the RSV Env glycoprotein was robustly recruited only to the homologous RSV budding sites. These data demonstrate that viral glycoproteins are not in preformed membrane patches prior to viral assembly but rather that glycoproteins are actively recruited to certain viral assembly sites.
Mutational Analysis of Conserved Amino Acids in the Influenza A Virus Nucleoprotein
Authors: Li Zejun , Watanabe Tokiko , Hatta Masato , Watanabe Shinji , Nanbo Asuka , Ozawa Makoto , Kakugawa Satoshi , Shimojima Masayuki , Yamada Shinya , Neumann Gabriele , Kawaoka Yoshihiro
Published: February 2009

The nucleoprotein (NP), which has multiple functions during the virus life cycle, possesses regions that are highly conserved among influenza A, B, and C viruses. To better understand the roles of highly conserved NP amino acids in viral replication, we conducted a comprehensive mutational analysis. Using reverse genetics, we attempted to generate 74 viruses possessing mutations at conserved amino acids of NP. Of these, 48 mutant viruses were successfully rescued; 26 mutants were not viable, suggesting a critical role of the respective NP amino acids in viral replication. To identify the step(s) in the viral life cycle that is impaired by these NP mutations, we examined viral-genome replication/transcription, NP localization, and incorporation of viral-RNA segments into progeny virions. We identified 15 amino acid substitutions in NP that inhibited viral-genome replication and/or transcription, resulting in significant growth defects of viruses possessing these substitutions. We also found several NP mutations that affected the efficient incorporation of multiple viral-RNA (vRNA) segments into progeny virions even though a single vRNA segment was incorporated efficiently. The respective conserved amino acids in NP may thus be critical for the assembly and/or incorporation of sets of eight vRNA segments.
Identification, synthesis and structural determination of some impurities of candesartan cilexetil
Authors: Havlíček Jaroslav , Mandelová Zuzana , Weisemann Ruediger , Střelec Ivo , Plaček Lukáš , Rádl Stanislav
Published: February 2009

All principal candesartan cilexetil impurities and/or degradation products were synthesized and identified. The differentiation of N-1 and N-2 ethylated candesartan cilexetil derivatives was performed using 1D and 2D NMR experiments. The influence of the magnetic field on the resolution and sensitivity of NMR experiments is shown. Selective hydrolysis of these compounds then provided corresponding producrs of hydrolysis of the ethoxy group.
Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction
Authors: Eitzen I , Holm I , Risberg M A
Published: February 2009

Objective:

To identify preoperative predictive factors for knee function two years after reconstructive surgery of the anterior cruciate ligament (ACL). The main hypothesis was that preoperative quadriceps strength would be the most significant predictor for knee function two years after reconstructive surgery.

Design:

Cohort study.

Setting:

ACL injured individuals treated at a University Hospital and an outpatient clinic in Oslo, Norway.

Participants:

Seventy-three individuals with complete unilateral rupture of the ACL scheduled for reconstruction with a bone-patellar-bone autograft were included in the study, from where 60 were available for two-year follow up and included in the final analyses.

Interventions:

Not applicable.

Main outcome measurements:

Identification of baseline independent variables that may predict knee function assessed with the Cincinnati Knee Score as dependent variable two years after ACL reconstruction.

Results:

Quadriceps muscle strength, meniscus injury and the Short-Form-36 Bodily Pain sub score were identified as significant predictors for knee function assessed from the Cincinnati Knee Score two years after ACL reconstruction. Individuals with preoperative quadriceps strength deficits above 20% also had persistent significantly larger strength deficits two years after surgery.

Conclusions:

Preoperative quadriceps muscle strength deficits and meniscus injuries have significant negative consequences for the long-term functional outcome after ACL reconstruction. From our findings we suggest that ACL reconstruction should not be performed before quadriceps muscle strength deficits of the injured limb is less than 20% of the uninjured limb.
The physiological regulation of pacing strategy during exercise: a critical review
Authors: Tucker R , Noakes T D
Published: February 2009

The regulation of the pacing strategy remains poorly understood, because much of classic physiology has focused on the factors that ultimately limit, rather than regulate, exercise performance. When exercise is self-paced and work rate is free to vary in response to external and internal physiological cues, then a complex system is proposed to be responsible for alterations in exercise intensity, possibly through altered activation of skeletal muscle motor units. The present review evaluates the evidence for such a complex system by investigating studies in which interventions such as elevated temperature, altered oxygen content of the air, reduced fuel availability and misinformation about distance covered have resulted in alterations to the pacing strategy. The review further investigates how such a pacing strategy might be regulated for optimal performance, while ensuring that irreversible physiological damage is not incurred.
Sociology of Sex Work
Authors: Weitzer Ronald
Published: February 2009

This review examines key dimensions of contemporary sex work, particularly prostitution. Most research focuses exclusively on street prostitution and female workers, with much less attention devoted to indoor prostitution, male and transgender workers, customers, and managers. Furthermore, most of the literature examines prostitution where it is illegal, neglecting contexts where it is legal and regulated by the government. The review demonstrates how research on these topics can enrich our understanding of contemporary sex work.
Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner
Authors: Molgat André SD , Gagnon AnneMarie , Sorisky Alexander
Published: February 2009

Obesity is associated with macrophage accumulation and inflammation in adipose tissue. Macrophage-secreted factors have been reported to inhibit the differentiation of preadipocytes into adipocytes and to modulate adipogenic extracellular matrix gene expression. To enlarge our understanding of macrophages and the scope of their interactions with preadipocytes, we investigated their effect on preadipocyte survival. Acute exposure of 3T3-L1 preadipocytes to J774A.1 macrophage-conditioned medium (MacCM) stimulated platelet-derived growth factor receptor (PDGFR) tyrosine phosphorylation by 4.1-fold. There were significant increases in the phosphocontent of downstream PDGFR targets Akt and ERK1/2 (5.3-fold and 2.4-fold, respectively) that were inhibited by PDGF immunoneutralization or by the selective PDGFR inhibitor imatinib. Serum-free J774A.1-MacCM or RAW264.7-MacCM completely prevented 3T3-L1 preadipocyte apoptosis normally induced by serum deprivation. Addition of PDGF alone to serum-free control medium was sufficient to prevent 3T3-L1 preadipocyte apoptosis. Inhibition of PDGFR activation by MacCM, either by addition of imatinib or by PDGF immunodepletion of MacCM, effectively disrupted the prosurvival effect. In summary, our data indicate that MacCM promotes preadipocyte survival in a PDGF-dependent manner.
Determination of apparent calcium affinity for endogenously expressed human sarco(endo)plasmic reticulum calcium-ATPase isoform SERCA3
Authors: Chandrasekera P. Charukeshi , Kargacin Margaret E. , Deans Julie P. , Lytton Jonathan
Published: February 2009

The sarco(endo)plasmic reticulum Ca2+-ATPases (SERCAs) play a crucial role in regulating free cytosolic Ca2+ concentration in diverse cell types. It has been shown that recombinant SERCA3, when measured in heterologous systems, exhibits low apparent affinity for Ca2+; however, Ca2+ affinity of native SERCA3 in an endogenous setting has not been examined. Such a measurement is complicated, because SERCA3 is always coexpressed with the housekeeping isoform SERCA2b. We used a fluorescence-based assay for monitoring continuous Ca2+ uptake into microsomes to examine the properties of endogenous human SERCA3 and SERCA2b. The kinetic parameters were derived using a cooperative two-component uptake model for Ca2+ activation, and the values assigned to SERCA3 were confirmed using the highly specific human SERCA3 inhibitory antibody PL/IM430. First, using recombinant human SERCA3 and SERCA2b proteins transiently expressed in HEK-293 cells, we confirmed the previously observed low apparent Ca2+ affinity for SERCA3 compared with SERCA2b (1.10 ± 0.04 vs. 0.26 ± 0.01 μM), and using mixtures of recombinant protein isoforms, we validated the two-component uptake model. Then we determined apparent Ca2+ affinity for SERCA proteins present endogenously in cultured Jurkat T lymphocytes and freshly isolated human tonsil lymphocytes. The apparent Ca2+ affinity in these two preparations was 1.04 ± 0.07 and 1.1 ± 0.2 μM for SERCA3 and 0.27 ± 0.02 and 0.26 ± 0.01 μM for SERCA2b, respectively. Our data demonstrate, for the first time, that affinity for Ca2+ is inherently lower for SERCA3 expressed in situ than for other SERCA isoforms.
l-NIL prevents renal microvascular hypoxia and increase of renal oxygen consumption after ischemia-reperfusion in rats
Authors: Legrand Matthieu , Almac Emre , Mik Egbert G. , Johannes Tanja , Kandil Aslı , Bezemer Rick , Payen Didier , Ince Can
Published: February 2009

Even though renal hypoxia is believed to play a pivotal role in the development of acute kidney injury, no study has specifically addressed the alterations in renal oxygenation in the early onset of renal ischemia-reperfusion (I/R). Renal oxygenation depends on a balance between oxygen supply and consumption, with the nitric oxide (NO) as a major regulator of microvascular oxygen supply and oxygen consumption. The aim of this study was to investigate whether I/R induces inducible NO synthase (iNOS)-dependent early changes in renal oxygenation and the potential benefit of iNOS inhibitors on such alterations. Anesthetized Sprague-Dawley rats underwent a 30-min suprarenal aortic clamping with or without either the nonselective NO synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) or the selective iNOS inhibitor l- N6-(1-iminoethyl)lysine hydrochloride (l-NIL). Cortical (CμPo2) and outer medullary (MμPo2) microvascular oxygen pressure (μPo2), renal oxygen delivery (Do2ren), renal oxygen consumption (V̇o2ren), and renal oxygen extraction (O2ER) were measured by oxygen-dependent quenching phosphorescence techniques throughout 2 h of reperfusion. During reperfusion renal arterial resistance and oxygen shunting increased, whereas renal blood flow, CμPo2, and MμPo2(−70, −42, and −42%, respectively, P < 0.05), V̇o2ren, and Do2ren(−70%, P < 0.0001, and −28%, P < 0.05) dropped. Whereas l-NAME further decreased Do2ren, V̇o2ren, CμPo2, and MμPo2and deteriorated renal function, l-NIL partially prevented the drop of Do2renand μPo2, increased O2ER, restored V̇o2renand metabolic efficiency, and prevented deterioration of renal function. Our results demonstrate that renal I/R induces early iNOS-dependent microvascular hypoxia in disrupting the balance between microvascular oxygen supply and V̇o2ren, whereas endothelial NO synthase activity is compulsory for the maintenance of this balance. l-NIL can prevent ischemic-induced renal microvascular hypoxia.
Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea
Authors: Oliven Ron , Tov Naveh , Odeh Majed , Gaitini Luis , Steinfeld Uri , Schwartz Alan R. , Oliven Arie
Published: February 2009

Both mandibular advancement (MA) and stimulation of the genioglossus (GG) have been shown to improve upper airway patency, but neither one achieves the effect of continuous positive airway pressure (CPAP) treatment. In the present study we assessed the combined effect of MA and GG stimulation on the relaxed pharynx in patients with obstructive sleep apnea (OSA). We evaluated responses of upper airway pressure-flow relationships and endoscopically determined pharyngeal cross-sectional area to MA and electrical stimulation of the GG in 14 propofol-anesthetized OSA patients. Measurements were undertaken at multiple levels of CPAP, enabling calculation of the critical closing pressure (Pcrit), upstream resistance (Rus), and pharyngeal compliance. GG stimulation, MA, and the combination of both shifted the pressure:flow relationships toward higher flow levels, resulting in progressively lower Pcrit (from baseline of 2.9 ± 2.2 to 0.9 ± 2.5, −1.4 ± 2.9, and −4.2 ± 3.3 cmH2O, respectively), without significant change in Rus. ΔPcrit during GG stimulation was significantly larger during MA than under baseline conditions (−2.8 ± 1.4 vs. −2.0 ± 1.4 cmH2O, P = 0.011). Combining the effect of GG stimulation with MA lowered Pcrit below 0 in all patients and restored pharyngeal patency to a level that enabled flow above the hypopnea level in 10/14 of the patients. Velopharyngeal compliance was not affected by either manipulation. We conclude that the combined effect of MA and GG stimulation is additive and may act in synergy, preventing substantial flow limitation of the relaxed pharynx in most OSA patients.
Relationship Between Adapted Neural Population Responses in MT and Motion Adaptation in Speed and Direction of Smooth-Pursuit Eye Movements
Authors: Yang Jin , Lisberger Stephen G.
Published: February 2009

We have asked how sensory adaptation is represented in the response of a population of visual motion neurons and whether the neural adaptation could drive behavioral adaptation. Our approach was to evaluate the effects of about 10 s of motion adaptation on both smooth-pursuit eye movements and the responses of neuron populations in extrastriate middle temporal visual area (MT) in awake monkeys. Stimuli for neural recordings consisted of patches of 100% correlated dot textures. There was a wide range of effects across neurons, but on average adaptation reduced the amplitude and width of the direction tuning curves of MT neurons, without large changes in the preferred direction. The effects were greatest when the direction of the adapting stimulus corresponded to the preferred direction of the MT neuron under study. Adaptation also reduced the amplitude of speed-tuning curves, again with the greatest effect when the adapting speed was equal to the preferred speed. The adapted tuning curves were shifted toward lower preferred speeds as the adapting speed increased. We constructed populations of model MT neurons based on our experimental sample and showed that the effects of adaptation on the direction and speed of pursuit eye movements were predicted when a variant of vector averaging decoded the responses of a subset of the neural population. We conclude that the effects of motion adaptation on the responses of MT neurons can support behavioral adaptation in pursuit eye movements.
Activation of Phosphatidylinositol-Linked Novel D1 Dopamine Receptors Inhibits High-Voltage-Activated Ca2+ Currents in Primary Cultured Striatal Neurons
Authors: Ma Li-Qun , Liu Chao , Wang Fang , Xie Na , Gu Jun , Fu Hui , Wang Jiang-Hua , Cai Fei , Liu Jue , Chen Jian-Guo
Published: February 2009

Recent evidences indicate the existence of a putative novel phosphatidylinositol (PI)-linked D1 dopamine receptor that mediates excellent anti-Parkinsonian but less severe dyskinesia action. To further understand the basic physiological function of this receptor in brain, the effects of a PI-linked D1 dopamine receptor-selective agonist 6-chloro-7,8-dihydroxy-3-methyl-1-(3-methylphenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF83959) on high-voltage activated (HVA) Ca2+ currents in primary cultured striatal neurons were investigated by whole cell patch-clamp technique. The results indicated that stimulation by SKF83959 induced an inhibition of HVA Ca2+ currents in a dose-dependent manner in substance-P (SP)-immunoreactive striatal neurons. Application of D1 receptor, but not D2, α1 adrenergic, 5-HT receptor, or cholinoceptor antagonist prevented SKF83959-induced reduction, indicating that a D1 receptor-mediated event assumed via PI-linked D1 receptor. SKF83959-induced inhibitory modulation was mediated by activation of phospholipase C (PLC), mobilization of intracellular Ca2+ stores and activation of calcineurin. Furthermore, the inhibitory effects were attenuated significantly by the L-type calcium channel antagonist nifedipine, suggesting that L-type calcium channels involved in the regulation induced by SKF83959. These findings may help to further understand the functional role of the PI-linked dopamine receptor in brain.