194 research outputs found
Functional characterization of synthetic leukotriene B and its stereochemical isomers.
Leukotriene B (LTB), a potent lipid chemotactic factor for neutrophils, is 5S,12R-dihydroxy-6,14-cis,8,10-trans-eicosatetraenoic acid (Fig 1), based upon direct comparison of natural LTB with synthetic 5S,12R-dihydroxy-6,8,10,14-eicosatetraenoic acid (5,12-di-HETE) stereoisomers in three biological assays. Of the six synthetic stereoisomers evaluated, only the 5S,12R,6,14-cis,8,10-trans compound had chemotactic potency for human neutrophils in vitro that was comparable to that of natural LTB, with a concentration of 3 X 10(9-9) M eliciting a one-half maximum response. In contrast, the racemic mixture of 5R,12R- and 5S,12S-6,10-trans,8,14-cis, the racemic mixture of 5S,12R- and 5R,12S-6,10-trans,8,14-cis, the 5S,12R-6,8-trans,10,14-cis, the 5S,12R-6,8,10-trans,14-cis, and the 5S,12S-6,8,10-trans,14-cis stereoisomers required concentrations of 3 X 10(-7) to 1 X 10(-6) M to elicit comparable responses. Only natural LTB and its synthetic counterpart elicited a local neutrophil infiltration when injected into the skin of the rhesus monkey at 10 ng and 100 ng per site. Natural and synthetic LTB at a concentration of 3 X 10(-8) M each provoked an EC25 contractile response of guinea pig pulmonary parenchymal strips in vitro, whereas the other four tested stereoisomers of 5,12-di-HETE were inactive at this concentration. Structure-function analyses suggest that the neutrophil chemotactic activity depends critically upon the C-1 to C-12 domain, including the stereochemistry of the 6-,8-,and 10-olefinic bonds and the presence of both hydroxyl groups
Laser excitation of the 1s-hyperfine transition in muonic hydrogen
The CREMA collaboration is pursuing a measurement of the ground-state
hyperfine splitting (HFS) in muonic hydrogen (p) with 1 ppm accuracy by
means of pulsed laser spectroscopy to determine the two-photon-exchange
contribution with relative accuracy. In the proposed
experiment, the p atom undergoes a laser excitation from the singlet
hyperfine state to the triplet hyperfine state, {then} is quenched back to the
singlet state by an inelastic collision with a H molecule. The resulting
increase of kinetic energy after the collisional deexcitation is used as a
signature of a successful laser transition between hyperfine states. In this
paper, we calculate the combined probability that a p atom initially in
the singlet hyperfine state undergoes a laser excitation to the triplet state
followed by a collisional-induced deexcitation back to the singlet state. This
combined probability has been computed using the optical Bloch equations
including the inelastic and elastic collisions. Omitting the decoherence
effects caused by {the laser bandwidth and }collisions would overestimate the
transition probability by more than a factor of two in the experimental
conditions. Moreover, we also account for Doppler effects and provide the
matrix element, the saturation fluence, the elastic and inelastic collision
rates for the singlet and triplet states, and the resonance linewidth. This
calculation thus quantifies one of the key unknowns of the HFS experiment,
leading to a precise definition of the requirements for the laser system and to
an optimization of the hydrogen gas target where p is formed and the laser
spectroscopy will occur.Comment: 21 pages, 4 figure
International Consensus Statement on Rhinology and Allergy: Rhinosinusitis
Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICARâRS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICARâRSâ2021 as well as updates to the original 140 topics. This executive summary consolidates the evidenceâbased findings of the document. Methods: ICARâRS presents over 180 topics in the forms of evidenceâbased reviews with recommendations (EBRRs), evidenceâbased reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICARâRSâ2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidenceâbased management algorithm is provided. Conclusion: This ICARâRSâ2021 executive summary provides a compilation of the evidenceâbased recommendations for medical and surgical treatment of the most common forms of RS
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