Much remains to be known about the mechanisms by which O(2)-dependent host defenses mediate broad antimicrobial activity.
We show herein that reactive nitrogen species (RNS) generated by inducible ...nitric oxide (NO) synthase (iNOS) account for the anti-Burkholderia mallei activity of IFNgamma-primed macrophages. Inducible NOS-mediated intracellular killing may represent direct bactericidal activity, because B. mallei showed an exquisite sensitivity to NO generated chemically. Exposure of B. mallei to sublethal concentrations of NO upregulated transcription of Fe-S cluster repair genes, while damaging the enzymatic activity of the Fe-S protein aconitase. To test whether Fe-S clusters are critical targets for RNS-dependent killing of B. mallei, a mutation was constructed in the NO-induced, Fe-S cluster repair regulator iscR. Not only was the iscR mutant hypersusceptible to iNOS-mediated killing, but its aconitase pool was readily oxidized by NO donors as compared to wild-type controls. Although killed by authentic H(2)O(2), which also oxidizes Fe-S clusters, B. mallei appear to be resilient to NADPH oxidase-mediated cytotoxicity. The poor respiratory burst elicited by this bacterium likely explains why the NADPH oxidase is nonessential to the killing of B. mallei while it is still confined within phagosomes.
Collectively, these findings have revealed a disparate role for NADPH oxidase and iNOS in the innate macrophage response against the strict aerobe B. mallei. To the best of our knowledge, this is the first instance in which disruption of Fe-S clusters is demonstrated as cause of the bactericidal activity of NO congeners.
Nitric oxide (NO*) is a critical component of mammalian host defense that is produced in macrophages and other cells comprising the innate immune system. Isolated mammalian macrophages have been ...utilized to measure the kinetics of NO production and to demonstrate NO-related antimicrobial actions. Some microorganisms possess enzymes to detoxify nitrogen oxides, and mutant strains lacking these enzymes can be used to demonstrate the importance of these mechanisms for intracellular bacterial survival. This chapter describes techniques with which to analyze the antimicrobial actions of nitric oxide in murine and human macrophages and in laboratory mice.
Germ‐free BALB/c mice, genetically engineered to be deficient for interleukin‐8 (IL‐8) receptor homolog (IL‐8Rh−/−), were more susceptible to gastric candidiasis after oral challenge and to acute ...systemic candidiasis after intravenous challenge than IL‐8Rh+/+ controls. In comparison to IL‐8Rh+/+ mice, the IL‐8Rh−/− mice had slower influx of polymorphonuclear neutrophils (PMN) into Candida albicans‐infected tissues and a lower percentage of PMN in peritoneal exudate cells (PEC) elicited with heat‐killed C. albicans. PEC from IL‐8Rh−/− mice exhibited less luminol‐dependent chemiluminescence in response to C. albicans and did not kill C. albicans hyphae as well as PEC from IL‐8Rh+/+ mice. C. albicans‐colonized IL‐8Rh−/− mice showed no histological evidence of systemic candidiasis. These results suggest a role for the IL‐8Rh in murine resistance to gastric and acute systemic candidiasis, but not in resistance to systemic candidiasis of endogenous origin. J. Leukoc. Biol. 66: 144–150; 1999.
In this thesis, I demonstrate Doppler and Sisyphus cooling of a cryogenic buffer-gas beam of CaH molecules. I detail the construction and optimization of the experimental apparatus, including the ...cryogenic source, laser systems, vacuum systems and detection schemes. I demonstrate that the cryogenic source produces a bright and slow beam of CaH molecules via ablation of a solid chemical target and thermalization with a He buffer gas. The molecular beam exits the ablation cell with an average forward velocity of 250 ±200 m/s and a molecular beam flux per ablation pulse of ≈ 1×1010 per steradian per pulse. I present the spectroscopic determination of the molecular transitions necessary to pursue laser cooling. These include the X2Σ+ → A2Π1/2 and the X2Σ+ → B2Σ+ transitions that each contain two spin-rotation states, J = 1/2 and J = 3/2, and a further pair of hyperfine states, F = 0,1 and F = 1,2, respectively. Finally, I describe the vibrational repumping transitions between the four hyperfine states of the J = 1/2 and J = 3/2 branches of the V = 1 vibrational state back to the ground state via decay from an intermediary state, X2Σ+(V = 1) → B2Σ+(V = 0) → X2Σ+(V = 0). I present measurements of the vibrational decay probabilities from the B2Σ+(V = 0) and A2Π1/2(V = 0) excited states to the V = 0,1 and 2 states of the ground X2Σ+ state. Next, I show that we can achieve a high scattering rate of ≈ 1.6E6 photons/second while cycling on the X2Σ+ → A2Π1/2 transition. Finally, I demonstrate the ability to perform transverse cooling of a beam of CaH molecules through both the Doppler mechanism and magnetically assisted Sisyphus mechanism. With the help of a transverse standing wave of laser light, I show that we are able to lower the molecular beam’s transverse temperature from 12.2±1.2 mK to 5.7±1.1mK. This thesis represents a promising start to laser slowing and magneto-optical trapping of CaH molecules, which could provide trapped ultracold samples of atomic hydrogen upon dissociation of the trapped CaH molecules.
Abstract A combination of measurements sensitive to the CKM angle γ from LHCb is performed. The inputs are from analyses of time-integrated B + arrow right DK +, B 0 arrow right DK 0, B 0 arrow right ...DK +pi- and B + arrow right DK +pi+pi- tree-level decays. In addition, results from a time-dependent analysis of B s 0 arrow rightD s K ± decays are included. The combination yields γ=(72.2 -7.3 +6.8 )°, where the uncertainty includes systematic effects. The 95.5% confidence level interval is determined to be γ 55.9, 85.2°. A second combination is investigated, also including measurements from B + arrow right Dpi+ and B + arrow right Dpi+pi-pi+ decays, which yields compatible results. Figure not available: see fulltext.
Two new algorithms for use in the analysis of Formula: see text collision are developed to identify the flavour of Formula: see text mesons at production using pions and protons from the ...hadronization process. The algorithms are optimized and calibrated on data, using Formula: see text decays from Formula: see text collision data collected by LHCb at centre-of-mass energies of 7 and 8 TeV . The tagging power of the new pion algorithm is 60% greater than the previously available one; the algorithm using protons to identify the flavour of a Formula: see text meson is the first of its kind.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract A measurement of the inclusive Z arrow right ττ cross-section in pp collisions at ... is presented based on a ...dataset of 1.0 fb^sup -1^ collected by the LHCb detector. Candidates for Z arrow right tau tau decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for Z bosons, with invariant mass between 60 and 120 GeV/c ^sup 2^, which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5, is measured to be sigma^sub pparrow rightZarrow rightττ^ = 71.4 ± 3.5 ± 2.8 ± 2.5 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for Z arrow right tau tau to Z arrow right mumu is determined to be 0.93 ± 0.09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements.Figure not available: see fulltext.
Our investigations show that nonlethal concentrations of nitric oxide (NO) abrogate the antibiotic activity of beta- lactam antibiotics against Burkholderia pseudomallei, Escherichia coli and ...nontyphoidal Salmonella enterica serovar Typhimurium. NO protects B. pseudomallei already exposed to beta-lactams, suggesting that this diatomic radical tolerizes bacteria against the antimicrobial activity of this important class of antibiotics. The concentrations of NO that elicit antibiotic tolerance repress consumption of oxygen (O.sub.2), while stimulating hydrogen peroxide (H.sub.2O.sub.2) synthesis. Transposon insertions in genes encoding cytochrome c oxidase-related functions and molybdenum assimilation confer B. pseudomallei a selective advantage against the antimicrobial activity of the beta-lactam antibiotic imipenem. Cumulatively, these data support a model by which NO induces antibiotic tolerance through the inhibition of the electron transport chain, rather than by potentiating antioxidant defenses as previously proposed. Accordingly, pharmacological inhibition of terminal oxidases and nitrate reductases tolerizes aerobic and anaerobic bacteria to beta-lactams. The degree of NO-induced beta-lactam antibiotic tolerance seems to be inversely proportional to the proton motive force (PMF), and thus the dissipation of DELTAH.sup.+ and DELTAPSI electrochemical gradients of the PMF prevents beta-lactam-mediated killing. According to this model, NO generated by IFNgammaprimed macrophages protects intracellular Salmonella against imipenem. On the other hand, sublethal concentrations of imipenem potentiate the killing of B. pseudomallei by NO generated enzymatically from IFNgamma-primed macrophages. Our investigations indicate that NO modulates the antimicrobial activity of beta-lactam antibiotics.
![Inactivation of [Fe-S] meta...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1932-6203/small "Inactivation of [Fe-S] metalloproteins mediates nitric oxide-dependent killing of Burkholderia mallei")
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