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Search Results: 1 - 10 of 410201 matches for " Jonathan M. Levine "
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Direct and Indirect Effects of Climate Change on a Prairie Plant Community
Peter B. Adler, James Leiker, Jonathan M. Levine
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006887
Abstract: Background Climate change directly affects species by altering their physical environment and indirectly affects species by altering interspecific interactions such as predation and competition. Recent studies have shown that the indirect effects of climate change may amplify or counteract the direct effects. However, little is known about the the relative strength of direct and indirect effects or their potential to impact population persistence. Methodology/Principal Findings We studied the effects of altered precipitation and interspecific interactions on the low-density tiller growth rates and biomass production of three perennial grass species in a Kansas, USA mixed prairie. We transplanted plugs of each species into local neighborhoods of heterospecific competitors and then exposed the plugs to a factorial manipulation of growing season precipitation and neighbor removal. Precipitation treatments had significant direct effects on two of the three species. Interspecific competition also had strong effects, reducing low-density tiller growth rates and aboveground biomass production for all three species. In fact, in the presence of competitors, (log) tiller growth rates were close to or below zero for all three species. However, we found no convincing evidence that per capita competitive effects changed with precipitation, as shown by a lack of significant precipitation × competition interactions. Conclusions/Significance We found little evidence that altered precipitation will influence per capita competitive effects. However, based on species' very low growth rates in the presence of competitors in some precipitation treatments, interspecific interactions appear strong enough to affect the balance between population persistence and local extinction. Therefore, ecological forecasting models should include the effect of interspecific interactions on population growth, even if such interaction coefficients are treated as constants.
Magnetic Resonance Imaging Lesions in the Central Nervous System of a Dog with Canine Monocytic Ehrlichiosis
Linda G. Lang,John F. Griffin,Jonathan M. Levine,Edward B. Breitschwerdt
Case Reports in Veterinary Medicine , 2011, DOI: 10.1155/2011/379627
Abstract: A ten-year-old neutered male dog was examined for tetraparesis, vestibular dysfunction, ataxia,and vertebral column hyperesthesia of 10 days duration. On magnetic resonance imaging (MRI),there were multifocal, punctate, T2-hyperintense lesions in the brain and cervical spinal cord andintracranial leptomeningeal contrast enhancement. Cerebrospinal fluid (CSF) analysis revealed apredominantly mononuclear pleocytosis and mildly elevated protein. Ehrlichia canis wasdiagnosed by serum immunofluorescent antibody (IFA) testing. The dog improved withadministration of doxycycline. This report describes MRI central nervous system findings in a dogwith ehrlichiosis.
H-NST Induces LEE Expression and the Formation of Attaching and Effacing Lesions in Enterohemorrhagic Escherichia coli
Jonathan A. Levine, Anne-Marie Hansen, Jane M. Michalski, Tracy H. Hazen, David A. Rasko, James B. Kaper
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0086618
Abstract: Background Enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli are important causes of morbidity and mortality worldwide. These enteric pathogens contain a type III secretion system (T3SS) responsible for the attaching and effacing (A/E) lesion phenotype. The T3SS is encoded by the locus of enterocyte effacement (LEE) pathogenicity island. The H-NS-mediated repression of LEE expression is counteracted by Ler, the major activator of virulence gene expression in A/E pathogens. A regulator present in EPEC, H-NST, positively affects expression of H-NS regulon members in E. coli K-12, although the effect of H-NST on LEE expression and virulence of A/E pathogens has yet-to-be determined. Results We examine the effect of H-NST on LEE expression and A/E lesion formation on intestinal epithelial cells. We find that H-NST positively affects the levels of LEE-encoded proteins independently of ler and induces A/E lesion formation. We demonstrate H-NST binding to regulatory regions of LEE1 and LEE3, the first report of DNA-binding by H-NST. We characterize H-NST mutants substituted at conserved residues including Ala16 and residues Arg60 and Arg63, which are part of a potential DNA-binding domain. The single mutants A16V, A16L, R60Q and the double mutant R60Q/R63Q exhibit a decreased effect on LEE expression and A/E lesion formation. DNA mobility shift assays reveal that these residues are important for H-NST to bind regulatory LEE DNA targets. H-NST positively affects Ler binding to LEE DNA in the presence of H-NS, and thereby potentially helps Ler displace H-NS bound to DNA. Conclusions H-NST induces LEE expression and A/E lesion formation likely by counteracting H-NS-mediated repression. We demonstrate that H-NST binds to DNA and identify arginine residues that are functionally important for DNA-binding. Our study suggests that H-NST provides an additional means for A/E pathogens to alleviate repression of virulence gene expression by H-NS to promote virulence capabilities.
Efficacy of a Metalloproteinase Inhibitor in Spinal Cord Injured Dogs
Jonathan M. Levine, Noah D. Cohen, Michael Heller, Virginia R. Fajt, Gwendolyn J. Levine, Sharon C. Kerwin, Alpa A. Trivedi, Thomas M. Fandel, Zena Werb, Augusta Modestino, Linda J. Noble-Haeusslein
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0096408
Abstract: Matrix metalloproteinase-9 is elevated within the acutely injured murine spinal cord and blockade of this early proteolytic activity with GM6001, a broad-spectrum matrix metalloproteinase inhibitor, results in improved recovery after spinal cord injury. As matrix metalloproteinase-9 is likewise acutely elevated in dogs with naturally occurring spinal cord injuries, we evaluated efficacy of GM6001 solubilized in dimethyl sulfoxide in this second species. Safety and pharmacokinetic studies were conducted in na?ve dogs. After confirming safety, subsequent pharmacokinetic analyses demonstrated that a 100 mg/kg subcutaneous dose of GM6001 resulted in plasma concentrations that peaked shortly after administration and were sustained for at least 4 days at levels that produced robust in vitro inhibition of matrix metalloproteinase-9. A randomized, blinded, placebo-controlled study was then conducted to assess efficacy of GM6001 given within 48 hours of spinal cord injury. Dogs were enrolled in 3 groups: GM6001 dissolved in dimethyl sulfoxide (n = 35), dimethyl sulfoxide (n = 37), or saline (n = 41). Matrix metalloproteinase activity was increased in the serum of injured dogs and GM6001 reduced this serum protease activity compared to the other two groups. To assess recovery, dogs were a priori stratified into a severely injured group and a mild-to-moderate injured group, using a Modified Frankel Scale. The Texas Spinal Cord Injury Score was then used to assess long-term motor/sensory function. In dogs with severe spinal cord injuries, those treated with saline had a mean motor score of 2 (95% CI 0–4.0) that was significantly (P<0.05; generalized linear model) less than the estimated mean motor score for dogs receiving dimethyl sulfoxide (mean, 5; 95% CI 2.0–8.0) or GM6001 (mean, 5; 95% CI 2.0–8.0). As there was no independent effect of GM6001, we attribute improved neurological outcomes to dimethyl sulfoxide, a pleotropic agent that may target diverse secondary pathogenic events that emerge in the acutely injured cord.
Immunogenicity and efficacy of oral vaccines in developing countries: lessons from a live cholera vaccine
Myron M Levine
BMC Biology , 2010, DOI: 10.1186/1741-7007-8-129
Abstract: Vaccines represent the epitome of a preventive strategy to control disease [1,2]. In the individual, they confer direct protection and, if high enough immunization coverage of a population is achieved, unimmunized people may also be protected, indirectly, through 'herd immunity' [3,4]. The strategic use of some vaccines, such as measles and polio vaccines, has interrupted indigenous transmission of those diseases in entire regions of the globe [5-8]. And one disease, smallpox, has been completely eradicated from the human population through the epidemiologically sound use of smallpox vaccine [9,10].In developing countries, where two-thirds of the world's population live, infectious diseases cause most of the mortality among children under 5 years of age [11] and constitute major health problems in older children and adults. Vaccines are among the most promising interventions to diminish the burden of specific infections in populations in developing countries [12-15].Oral vaccines are particularly attractive for immunizing populations in developing countries for several reasons. First, contaminated needles and syringes are major problems both for health workers and for environmental safety in many developing countries where there is a high prevalence of HIV and hepatitis B and C [16-18]. Because they obviate the need for needles and syringes, oral vaccines allow less qualified health workers to carry out immunization. Second, the simple logistics of oral vaccines are highly compatible with mass immunization campaigns [19,20]. Lastly, in most societies both adults and children generally prefer an oral vaccine to a parenteral injection.Despite the attractions of oral vaccines for developing countries, many oral vaccines, both live and non-living, have proven to be less immunogenic or less protective when administered to infants, children or adults living in low socioeconomic conditions in less-developed countries than they are when used in industrialized countries (Tab
Letters to the Editor
Elliott M. Levine
Infectious Diseases in Obstetrics and Gynecology , 2001, DOI: 10.1155/s1064744901000114
Outbursts, State Transitions, and Periodicities Observed with the RXTE All-Sky Monitor
Alan M. Levine
Physics , 1998, DOI: 10.1016/S0920-5632(98)00208-4
Abstract: Results from the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer are reviewed. A number of recurrent transient sources have been detected, while only a few previously unreported sources have been discovered. The ASM light curves show a wide variety of phenomena in general, and, in particular, those of transient sources show a wide range of properties. Examples are used to illustrate that the distinction between persistent and transient sources may be very unclear. The results of searches for periodicities in the ASM light curves are summarized, and other astrophysical investigations using ASM light curves are suggested. The latter include investigations of the possible causes of long-term quasiperiodic and chaotic variability, and comparative studies on the basis of the observed variability.
Algebraic cobordism revisited
M. Levine,R. Pandharipande
Mathematics , 2006,
Abstract: We define a cobordism theory in algebraic geometry based on normal crossing degenerations with double point singularities. The main result is the equivalence of double point cobordism to the theory of algebraic cobordism previously defined by Levine and Morel. Double point cobordism provides a simple, geometric presentation of algebraic cobordism theory. As a corollary, the Lazard ring given by products of projective spaces rationally generates all nonsingular projective varieties modulo double point degenerations. Double point degenerations arise naturally in relative Donaldson-Thomas theory. We use double point cobordism to prove all the degree 0 conjectures in Donaldson-Thomas theory: absolute, relative, and equivariant.
Multiwavelength Observations of the Candidate Disintegrating sub-Mercury KIC 12557548b
Bryce Croll,Saul Rappaport,John DeVore,Ronald L. Gilliland,Justin R. Crepp,Andrew W. Howard,Kimberly M. Star,Eugene Chiang,Alan M. Levine,Jon M. Jenkins,Loic Albert,Aldo S. Bonomo,Jonathan J. Fortney,Howard Isaacson
Physics , 2014, DOI: 10.1088/0004-637X/786/2/100
Abstract: We present multiwavelength photometry, high angular resolution imaging, and radial velocities, of the unique and confounding disintegrating low-mass planet candidate KIC 12557548b. Our high angular resolution imaging, which includes spacebased HST/WFC3 observations in the optical, and groundbased Keck/NIRC2 observations in K'-band, allow us to rule-out background and foreground candidates at angular separations greater than 0.2 arcsec that are bright enough to be responsible for the transits we associate with KIC 12557548. Our radial velocity limit from Keck/HIRES allows us to rule-out bound, low-mass stellar companions to KIC 12557548 on orbits less than 10 years, as well as placing an upper-limit on the mass of the candidate planet of 1.2 Jupiter masses; therefore, the combination of our radial velocities, high angular-resolution imaging, and photometry are able to rule-out most false positive interpretations of the transits. Our precise multiwavelength photometry includes two simultaneous detections of the transit of KIC 12557548b using CFHT/WIRCam at 2.15 microns and the Kepler space telescope at 0.6 microns, as well as simultaneous null-detections of the transit by Kepler and HST/WFC3 at 1.4 microns. Our simultaneous HST/WFC3 and Kepler null-detections, provide no evidence for radically different transit depths at these wavelengths. Our simultaneous CFHT/WIRCam detections in the near-infrared and with Kepler in the optical reveal very similar transit depths (the average ratio of the transit depths at ~2.15 microns compared to ~0.6 microns is: 1.02 +/- 0.20). This suggests that if the transits we observe are due to scattering from single-size particles streaming from the planet in a comet-like tail, then the particles must be ~0.5 microns in radius or larger, which would favor that KIC 12557548b is a sub-Mercury, rather than super-Mercury, mass planet.
Gauging U.S. Emergency Medical Services Workers' Willingness to Respond to Pandemic Influenza Using a Threat- and Efficacy-Based Assessment Framework
Daniel J. Barnett,Roger Levine,Carol B. Thompson,Gamunu U. Wijetunge,Anthony L. Oliver,Melissa A. Bentley,Patrick D. Neubert,Ronald G. Pirrallo,Jonathan M. Links,Ran D. Balicer
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009856
Abstract: Emergency Medical Services workers' willingness to report to duty in an influenza pandemic is essential to healthcare system surge amidst a global threat. Application of Witte's Extended Parallel Process Model (EPPM) has shown utility for revealing influences of perceived threat and efficacy on non-EMS public health providers' willingness to respond in an influenza pandemic. We thus propose using an EPPM-informed assessment of EMS workers' perspectives toward fulfilling their influenza pandemic response roles.
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