9,597 research outputs found
High levels of cyclic di-GMP in Klebsiella pneumoniae attenuate virulence in the lung
ABSTRACT
The bacterial second messenger bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) has been shown to influence the expression of virulence factors in certain pathogenic bacteria, but little is known about its activity in the increasingly antibiotic-resistant pathogen
Klebsiella pneumoniae
. Here, the expression in
K. pneumoniae
of a heterologous diguanylate cyclase increased the bacterial c-di-GMP concentration and attenuated pathogenesis in murine pneumonia. This attenuation remained evident in mice lacking the c-di-GMP sensor STING, indicating that the high c-di-GMP concentration exerted its influence not on host responses but on bacterial physiology. While serum resistance and capsule expression were unaffected by the increased c-di-GMP concentration, both type 3 and type 1 pili were strongly upregulated. Importantly, attenuation of
K. pneumoniae
virulence by high c-di-GMP levels was abrogated when type 1 pilus expression was silenced. We conclude that increased type 1 piliation may hamper
K. pneumoniae
virulence in the respiratory tract and that c-di-GMP signaling represents a potential therapeutic target for antibiotic-resistant
K. pneumoniae
in this niche.
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Sling Complications
https://digitalscholarship.unlv.edu/wrin_briefs/1003/thumbnail.jp
Automated progress identification and feedback in large experimental laboratories
In this work we describe a novel web-based system whose aim is to enhance the learning environment within experimental laboratories, and report on its deployment in undergraduate computer architecture modules. Student progress is tracked and recorded throughout the practical work, and supervisory facilities are provided including the visualisation of the progress of everyone in the laboratory on a management console. The system delivers information concerning the practical work to be undertaken, and uses carefully designed sets of questions based on the observations to be made by students in the laboratory. The responses made in this system are used to feedback further specific information to the student to aid their individual progress
Surgeon Volume
https://digitalscholarship.unlv.edu/wrin_briefs/1002/thumbnail.jp
Incentives vs. Control: An Analysis of U.S. Dual-Class Companies
Dual-class common stock allows for the separation of voting rights and cash flow rights across the different classes of equity. We construct a large sample of dual-class firms in the United States and analyze the relationships of insider's cash flow rights and voting rights with firm value, performance, and investment behavior. We find that relationship of firm value to cash flow rights is positive and concave and the relationship to voting rights is negative and convex. Identical quadratic relationships are found for the respective ownership variables with sales growth, capital expenditures, and the combination of R&D and advertising. Our evidence is consistent with an entrenchment effect of voting control that leads managers to underinvest and an incentive effect of cash flow ownership that induces managers to pursue more aggressive strategies.
Is a step in the primordial spectral index favored by CMB data ?
A sudden small change in the second derivative of the inflaton potential can
result in a universal local feature in the spectrum of primordial perturbations
generated during inflation. The exact solution describing this feature
\cite{minu} is characterized by a step in the spectral index modulated by
characteristic oscillations and results in a large running of the spectral
index localized over a few e-folds of scale. In this paper we confront this
step-like feature with the 5 year WMAP results and demonstrate that it provides
a better fit to this data than a featureless initial spectrum. If such a
feature exists at all, then it should lie at sufficiently large scales corresponding to . The sign of
the effect is shown to correspond to the negative running of localized
near this scale. This feature could arise as a result of a
`mini-waterfall'-type fast second order phase transition experienced by an
auxiliary heavy field during inflation, in a model similar to hybrid inflation
(though for a different choice of parameters). If this is the case, then the
auxiliary field should be positively coupled to the inflaton.Comment: Several new results, figures and enhanced discussion. Main
conclusions unchanged. Matches the final version to be published in JCA
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