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Search Results: 1 - 10 of 256125 matches for " David G Song "
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A Modeling-Derived Hypothesis on Chronicity in Respiratory Diseases: Desensitized Pathogen Recognition Secondary to Hyperactive IRAK/TRAF6 Signaling
Tingting Zhang, Kyung W. Song, Mohammad Hekmat-Nejad, David G. Morris, Brian R. Wong
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005332
Abstract: Several chronic respiratory diseases exhibit hyperactive immune responses in the lung: abundant inflammatory mediators; infiltrating neutrophils, macrophages, lymphocytes and other immune cells; and increased level of proteases. Such diseases include cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD) and severe/neutrophilic asthma. Paradoxically, patients with these diseases are also susceptible to detrimental bacterial infection and colonization. In this paper, we seek to explain how a positive feedback mechanism via IL-8 could lead to desensitization of epithelial cells to pathogen recognition thus perpetuating bacterial colonization and chronic disease states in the lung. Such insight was obtained from mathematical modeling of the IRAK/TRAF6 signaling module, and is consistent with existing clinical evidence. The potential implications for targeted treatment regimes for these persistent respiratory diseases are explored.
Adaptive Millimeter Wave Beam Alignment for Dual-Polarized MIMO Systems
Jiho Song,Junil Choi,Stephen G. Larew,David J. Love,Timothy A. Thomas,Amitava Ghosh
Mathematics , 2014,
Abstract: Fifth generation wireless systems are expected to employ multiple antenna communication at millimeter wave (mmWave) frequencies using small cells within heterogeneous cellular networks. The high path loss of mmWave as well as physical obstructions make communication challenging. To compensate for the severe path loss, mmWave systems may employ a beam alignment algorithm that facilitates highly directional transmission by aligning the beam direction of multiple antenna arrays. This paper discusses a mmWave system employing dual-polarized antennas. First, we propose a practical soft-decision beam alignment (soft-alignment) algorithm that exploits orthogonal polarizations. By sounding the orthogonal polarizations in parallel, the equality criterion of the Welch bound for training sequences is relaxed. Second, the analog beamforming system is adapted to the directional characteristics of the mmWave link assuming a high Ricean K-factor and poor scattering environment. The soft-algorithm enables the mmWave system to align innumerable narrow beams to channel subspace in an attempt to effectively scan the mmWave channel. Thirds, we propose a method to efficiently adapt the number of channel sounding observations to the specific channel environment based on an approximate probability of beam misalignment. Simulation results show the proposed soft-alignment algorithm with adaptive sounding time effectively scans the channel subspace of a mobile user by exploiting polarization diversity.
Cysteine 904 Is Required for Maximal Insulin Degrading Enzyme Activity and Polyanion Activation
Eun Suk Song, Manana Melikishvili, Michael G. Fried, Maria A. Juliano, Luiz Juliano, David W. Rodgers, Louis B. Hersh
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046790
Abstract: Cysteine residues in insulin degrading enzyme have been reported as non-critical for its activity. We found that converting the twelve cysteine residues in rat insulin degrading enzyme (IDE) to serines resulted in a cysteine-free form of the enzyme with reduced activity and decreased activation by polyanions. Mutation of each cysteine residue individually revealed cysteine 904 as the key residue required for maximal activity and polyanion activation, although other cysteines affect polyanion binding to a lesser extent. Based on the structure of IDE, Asn 575 was identified as a potential hydrogen bond partner for Cys904 and mutation of this residue also reduced activity and decreased polyanion activation. The oligomerization state of IDE did not correlate with its activity, with the dimer being the predominant form in all the samples examined. These data suggest that there are several conformational states of the dimer that affect activity and polyanion activation.
Measurement of Hepatic Protein Fractional Synthetic Rate with Stable Isotope Labeling Technique in Thapsigargin Stressed HepG2 Cells
Juquan Song, Xiao-jun Zhang, Darren Boehning, Natasha C. Brooks, David N. Herndon, Marc G. Jeschke
International Journal of Biological Sciences , 2012,
Abstract: Severe burn-induced liver damage and dysfunction is associated with endoplasmic reticulum (ER) stress. ER stress has been shown to regulate global protein synthesis. In the current study, we induced ER stress in vitro and estimated the effect of ER stress on hepatic protein synthesis. The aim was two-fold: (1) to establish an in vitro model to isotopically measure hepatic protein synthesis and (2) to evaluate protein fractional synthetic rate (FSR) in response to ER stress. Human hepatocellular carcinoma cells (HepG2) were cultured in medium supplemented with stable isotopes 1,2-13C2-glycine and L-[ring-13C6]phenylalanine. ER stress was induced by exposing the cells to 100 nM of thapsigargin (TG). Cell content was collected from day 0 to 14. Alterations in cytosolic calcium were measured by calcium imaging and ER stress markers were confirmed by Western blotting. The precursor and product enrichments were detected by GC-MS analysis for FSR calculation. We found that the hepatic protein FSR were 0.97±0.02 and 0.99±0.05%/hr calculated from 1,2-13C2-glycine and L-[ring-13C6]phenylalanine, respectively. TG depleted ER calcium stores and induced ER stress by upregulating p-IRE-1 and Bip. FSR dramatically decreased to 0.68±0.03 and 0.60±0.06%/hr in the TG treatment group (p<0.05, vs. control). TG-induced ER stress inhibited hepatic protein synthesis. The stable isotope tracer incorporation technique is a useful method for studying the effects of ER stress on hepatic protein synthesis.
Mutations in FLS2 Ser-938 Dissect Signaling Activation in FLS2-Mediated Arabidopsis Immunity
Yangrong Cao,David J. Aceti,Grzegorz Sabat,Junqi Song,Shin-ichi Makino,Brian G. Fox,Andrew F. Bent
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003313
Abstract: FLAGELLIN-SENSING 2 (FLS2) is a leucine-rich repeat/transmembrane domain/protein kinase (LRR-RLK) that is the plant receptor for bacterial flagellin or the flagellin-derived flg22 peptide. Previous work has shown that after flg22 binding, FLS2 releases BIK1 kinase and homologs and associates with BAK1 kinase, and that FLS2 kinase activity is critical for FLS2 function. However, the detailed mechanisms for activation of FLS2 signaling remain unclear. The present study initially identified multiple FLS2 in vitro phosphorylation sites and found that Serine-938 is important for FLS2 function in vivo. FLS2-mediated immune responses are abolished in transgenic plants expressing FLS2S938A, while the acidic phosphomimic mutants FLS2S938D and FLS2S938E conferred responses similar to wild-type FLS2. FLS2-BAK1 association and FLS2-BIK1 disassociation after flg22 exposure still occur with FLS2S938A, demonstrating that flg22-induced BIK1 release and BAK1 binding are not sufficient for FLS2 activity, and that Ser-938 controls other aspects of FLS2 activity. Purified BIK1 still phosphorylated purified FLS2S938A and FLS2S938D mutant kinase domains in vitro. Phosphorylation of BIK1 and homologs after flg22 exposure was disrupted in transgenic Arabidopsis thaliana plants expressing FLS2S938A or FLS2D997A (a kinase catalytic site mutant), but was normally induced in FLS2S938D plants. BIK1 association with FLS2 required a kinase-active FLS2, but FLS2-BAK1 association did not. Hence FLS2-BIK1 dissociation and FLS2-BAK1 association are not sufficient for FLS2-mediated defense activation, but the proposed FLS2 phosphorylation site Ser-938 and FLS2 kinase activity are needed both for overall defense activation and for appropriate flg22-stimulated phosphorylation of BIK1 and homologs.
A Causal Set Black Hole
Song He,David Rideout
Physics , 2008, DOI: 10.1088/0264-9381/26/12/125015
Abstract: We explicitly compute the causal structure of the Schwarzschild black hole spacetime, by providing an algorithm to decide if any pair of events is causally related. The primary motivation for this study comes from discrete quantum gravity, in particular the causal set approach, in which the fundamental variables can be thought of as the causal ordering of randomly selected events in spacetime. This work opens the way to simulating non-conformally flat spacetimes within the causal set approach, which may allow one to study important questions such as black hole entropy and Hawking radiation on a full four dimensional causal set black hole.
Inventories, Interest Rates, and Markups  [PDF]
David G. Bivin
Theoretical Economics Letters (TEL) , 2011, DOI: 10.4236/tel.2011.12010
Abstract: This note explains why inventories might rise with interest rates. Higher real interest rates not only increase the carrying cost of inventories they also reduce the present value of the markup on delayed sales. When the markup is large enough, it is profitable to increase stocks in order to avoid sales delays. Another possibility is that the firm has an incentive to smooth its total stocks so that an increase in the real interest rate causes finished goods to fall but the reduction is partially offset by an increase in raw materials.
The Moon Meets All Requirements of the IAU Definition for “Planet”  [PDF]
David G. Russell
International Journal of Astronomy and Astrophysics (IJAA) , 2017, DOI: 10.4236/ijaa.2017.74024
Abstract: The Earth-Moon system has often been characterized as having some characteristics of a “double planet” system. It is demonstrated that while the orbital barycenter of the Earth-Moon pair lies inside the radius of the Earth, the Moon does meet all three requirements of the IAU definition for “planet” and therefore the Moon can correctly be identified as the Solar System’s 9th planet. In order to avoid confusion by this development it is necessary to add definitions for “double planet”, “double dwarf planet”, “satellite planet”, and “satellite” to complement the International Astronomical Union definitions for “planet” and “dwarf planet”. The Earth-Moon system meets the requirements of a “double planet” system while the Pluto-Charon system meets the requirements of a “double dwarf planet” system. In order to extrapolate sub-stellar taxonomy to exoplanetary systems, general formation mechanisms (star-like gas collapse in molecular clouds vs. proto-planetary disk formation) should be included in the definitions for the various classes of sub-stellar mass bodies.
Metabotropic glutamate receptor 5 (mGluR5) regulates bladder nociception
Lara W Crock, Kristina M Stemler, David G Song, Philip Abbosh, Sherri K Vogt, Chang-Shen Qiu, H Henry Lai, Indira U Mysorekar, Robert W Gereau IV
Molecular Pain , 2012, DOI: 10.1186/1744-8069-8-20
Abstract: Using a combination of genetic and pharmacologic approaches, we provide evidence indicating that mGluR5 is necessary for the full expression of VMR in response to bladder distention in the absence of inflammation. Furthermore, we observed that mice infected with a uropathogenic strain of Escherichia coli (UPEC) develop inflammatory hyperalgesia to bladder distention, and that the selective mGluR5 antagonist fenobam [N-(3-chlorophenyl)-N'-(4,5-dihydro-1-methyl-4-oxo-1H-imidazole-2-yl) urea], reduces the VMR to bladder distention in UPEC-infected mice.Taken together, these data suggest that mGluR5 modulates both inflammatory and non-inflammatory bladder nociception, and highlight the therapeutic potential for mGluR5 antagonists in the alleviation of bladder pain.Interstitial cystitis/painful bladder syndrome (IC/PBS) is a serious and painful condition of unknown etiology that affects 3-6% of women in the United States [1,2]. The major clinical symptom of IC/PBS is pain upon bladder filling (distention) leading to urinary frequency and urinary urgency [3]. The current available treatments are often ineffective and do not treat the underlying pathology. Rodent bladder-injury models that induce some of the symptoms observed in IC/PBS have been used to evaluate potential treatments for IC/PBS [4-9]. One injury model, bacterial cystitis (urinary tract infection, UTI) is known to cause a similar constellation of symptoms as observed in IC/PBS (i.e. urinary frequency and urgency [10-12]). In addition, bacterial cystitis can be modeled in rodents through bladder exposure to uropathogenic Escherichia Coli (UPEC) [13,14]. Bladder infections due to UPEC are responsible for approximately 80% of UTIs in otherwise healthy women [15,16]. Understanding the underlying molecular mechanisms of both non-inflammatory bladder pain and inflammatory bladder pain due to UPEC infection could lead to the development of novel treatments for painful bladder infections as well as for IC/PBS and po
Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Singly-Ionized Lead
Negar Heidarian,Richard E. Irving,Adam. M. Ritchey,Steven R. Federman,David. G. Ellis,Song Cheng,Larry J. Curtis,Walter A. Furman
Physics , 2015, DOI: 10.1088/0004-637X/808/2/112
Abstract: We present the results of lifetime measurements made using beam-foil techniques on levels of astrophysical interest in Pb II producing lines at 1203.6 A ($6s6p^{2}$ $^{2}D_{3/2}$) and 1433.9 A ($6s^{2}6d$ $^{2}D_{3/2}$). We also report the first detection of the Pb II $\lambda1203$ line in the interstellar medium (ISM) from an analysis of archival spectra acquired by the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). The oscillator strengths derived from our experimental lifetimes for Pb II $\lambda\lambda1203$, $1433$ are generally consistent with recent theoretical results, including our own relativistic calculations. Our analysis of high-resolution HST/STIS spectra helps to confirm the relative strengths of the Pb II $\lambda\lambda 1203$, $1433$ lines. However, the oscillator strength that we obtain for Pb II $\lambda1433$ ($0.321\pm0.034$) is significantly smaller than earlier theoretical values, which have been used to study the abundance of Pb in the ISM. Our revised oscillator strength for $\lambda1433$ yields an increase in the interstellar abundance of Pb of 0.43 dex over determinations based on the value given by Morton, indicating that the depletion of Pb onto interstellar dust grains is less severe than previously thought.
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