1,720,961 research outputs found
Exploring pyrazinamide derivatives as novel Pseudomonas aeruginosa inhibitors: unexploited antibacterial molecules for a new antibiotics target
No full textBackground and Rationale
P. aeruginosa is the most common pathogen in cystic fibrosis lung infection with a high negative impact on lung functionality and patients’ mortality. The increasing diffusion of multi-resistant strains demands for the development of new anti-Pa agents. The ribosomal protein S1 (encoded by rpsA) is a promising target for new antibacterial drugs. In Escherichia coli, S1 has an essential role in translation. S1 is highly conserved among Gram negative bacteria and absent in mammalian cells. Recently, it has been found that pyrazinamide (PZA), a first-line tuberculosis drug, targets S1 protein. PZA derivatives were developed by Bracco SpA in the early ‘60s and roughly characterized for antibacterial activity; interestingly, in preliminary tests, the derivative B2320 seemed to be active against Pseudomonas aeruginosa (Pa). B2320 target in Pa is currently unknown.
Hypothesis and objectives
1. Characterizing the anti-Pa activity of B2320.
2. Exploring Pa S1 as a potential target for new antibacterials.
3. Setting-up an E. coli biosensor strain for the screening of S1 inhibitors.
Results and their significance
1. B2320 has been tested for anti-bacterial activity both against Pseudomonas lab strains and a collection of clinical isolates from CF patients in different growth conditions. We found that although only high concentrations of B2320 impaired aerobic growth of most P. aeruginosa strains, the sensitivity to B2320 was increased by stress conditions and in vivo, in the infection model Galleria mellonella. The genome of a clinical isolate particularly sensitive to B2320 and of a B2320-resistant derivative were sequenced.
2. rpsA essentiality in P. aeruginosa has been addressed by site-directed mutagenesis. Our data strongly support rpsA essentiality in P. aeruginosa.
3. We have set up a fluorescence-based assay to find inhibitors of S1-dependent translation initiation in E. coli. The screen allows to identify compounds interfering with an essential and bacteria specific step of gene expression, discriminating from molecules with nonspecific cell toxicity. Moreover, as we have adapted the assay to P. aeruginosa, cell penetration properties of the active compounds identified in the primary screening could be easily assessed. Since our screen is technically very simple and appears to be robust, it is potentially adaptable to High-Throughput-Screening campaigns
A whole-cell assay for specific inhibitors of translation initiation in bacteria
No full textThe bacterial translational apparatus is an ideal target for the search of new antibiotics. In fact, it performs an essential process carried out by a large number of potential subtargets for antibiotic action. Moreover, it is sufficiently different in several molecular details from the apparatus of Eukarya and Archaea to generally ensure specificity for the bacterial domain. This applies in particular to translation initiation, which is the most different step in the process. In bacteria, the 30S ribosomal subunit directly binds to the translation initiation region, a site within the messenger RNA (mRNA) 5'-untranslated region (5'-UTR). 30S binding is mediated by the interaction of both the 16S ribosomal RNA and the ribosomal protein S1 with specific regions of the mRNA 5'-UTR. An alternative, S1-independent pathway is enjoyed by leaderless mRNAs (i.e., transcripts devoid of a 5'-UTR). We have developed a simple fluorescence-based whole-cell assay in Escherichia coli to find inhibitors of the canonical S1-dependent translation initiation pathway. The assay has been set up both in a common E. coli laboratory strain and in a strain with an outer membrane permeability defect. Compared with other whole-cell assays for antibacterials, the major advantages of the screen described here are high sensitivity and specificity
Exploring pyrazinamide derivatives as novel Pseudomonas aeruginosa inhibitors: unexploited antibacterial molecules for a new antibiotics target
No full textBackground
The ribosomal protein S1 (encoded by rpsA) is a promising target for new antibacterial drugs. In Escherichia coli, S1 has an essential role in translation. S1 is highly conserved among Gram negative bacteria and absent in mammalian cells. Recently, it has been found that pyrazinamide (PZA), a first-line tuberculosis drug, targets S1 protein. PZA derivatives were developed by Bracco SpA in the early ‘60s and roughly characterized for antibacterial activity; interestingly, in preliminary tests, the derivative B2320 seemed to be active against Pseudomonas aeruginosa (Pa). B2320 target in Pa is currently unknown.
Hypothesis and objectives
1. Characterizing the anti-Pa activity of B2320.
2. Exploring Pa S1 as a potential target for new antibacterials.
3. Setting-up an E. coli biosensor strain for the screening of S1 inhibitors.
Essential methods
1. B2320 will be tested for anti-bacterial activity both against Pseudomonas lab strains and a collection of clinical isolates from cystic fibrosis patients. The mechanism of action of the compound will be investigated.
2. A Pa strain with rpsA conditional expression will be constructed in order to assess its essentiality.
3. A fluorescence-based assay to find inhibitors of S1-dependent translation initiation will be set up in E. coli, transferred in Pa and used to screen a collection of heterogeneous chemical compounds for translation inhibitors.
Preliminary results
1. B2320 activity against PAO1 and PA14 lab strains has been tested in different growth conditions. Interestingly, the more virulent PA14 strain seems more sensitive to B2320 than PAO1 strain.
2. The mutant is under construction. We have mapped the 5’-end of rpsA transcript in Pa. This has been instrumental in designing the construct for rpsA mutation.
3. We have developed a simple whole-cell assay in E. coli that allows discriminating antibiotics inhibiting different translation steps.
Expected results and their significance
P. aeruginosa is the most common pathogen in CF lung infection with a high negative impact on lung functionality and patients’ mortality. The increasing diffusion of multi-resistant strains demands for the development of new anti-Pa agents. These could be identified both among PZA derivatives and by our whole-cell screening of libraries of chemical compounds. Moreover, if Pa S1 will result to be essential as expected, it would be a robust target for the design of new drugs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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