1,720,975 research outputs found
A plasmid-linked caseinolytic activity in Enterobacteriaceae.
No full textWe have tested for production of caseinolytic activity the strain of E. coli K12 J62 carrying different R factors from various Enterobacteriaceae of clinical isolates. The results obtained showed the presence of a caseinolytic activity in 7 out of 139 R factors tested. All of these positive (cas+) R factors derived from strains of Klebsiella pneumoniae and all were able to transfer a strong lac+ phenotype as well as multiple antibiotic resistances (R-lac factors). Another strain of E. coli K12, J53, which is plasmid-free, produced levels of caseinolytic activity comparable to those of the Klebsiella R factors; J62, on the contrary, appeared to possess an inhibitor specific for the caseinolytic activities of J53 and of the R factors but not of other cas+ Gram+ and Gram- organisms. The hypothesis that the expression of the cas+ phenotype in E. coli K12 may be due to the presence of plasmid-linked regulatory genes is discussed
Degradation of human fibronectin by strains of E. coli K12 carrying R factors from Klebsiella pneumoniae.
No full textWe studied the ability to degrade human fibronectin by strains of E. coli K12 carrying R factors from Klebsiella pneumoniae, previously shown to possess a caseinolytic activity. The preliminary data obtained showed that at least two of these R+ strains are able to degrade fibronectin to small peptides retaining the gelatin-binding site of the molecule. We also found indications of non-fibronectin gelatin-binding polypeptides secreted by the strains tested into the culture broth. The possible significance of this bacterial property as a factor of pathogenicity is discussed
R factor-mediated adhesiveness to mammalian cells in E. coli K12.
No full textWe checked the possible effects of the standard plasmids of known compatibility groups on the ability of three strains of E. coli K12, J62, J53 and C600, to agglutinate human and guinea pig erythrocytes and to adhere to cultures of human epithelial cells. The results obtained showed that under defined experimental conditions one plasmid, R478, from a clinical isolate of Serratia marcescens is able to modulate the adhesive properties of the strain J62 which lacks adhesiveness. On the contrary, the same factor did not alter the ability of strains J53 and C600 to agglutinate erythrocytes and to adhere to human epithelial cells in culture, nor did it induce adhesive properties in wild-type strains of E. coli from clinical isolates that lacked them. This would suggest a possible plasmidic control of chromosomally encoded surface structures that mediated adhesiveness of E. coli to mammalian cells
Bovine leukemia virus inhibiting activity in fetal calf serum.
No full textWe have obtained a new cell line persistently infected with bovine leukemia virus (BLV). BLV-infected cells can be easily detected by indirect immunofluorescence or immunoperoxidase staining technique. The morphology and number of infected cells seem to be related to serum concentration in culture medium: fetal calf serum (FCS) showed a marked effect on virus growth and virus distribution in cell cultures. All of the commercial lots of FCS tested showed BLV inhibiting activity very similar to that previously described for other viruses
Urokinase plasminogen activator and gelatinases are associated with membrane vesicles shed by human HT-1080 fibrosarcoma cells
No full textGoing 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
Relationship between beta-lactamases production and resistance to beta-lactam antibiotics in clinical isolates of Enterobacteriaceae.
No full text288 clinical isolates of Enterobacteriaceae were assayed for beta-lactamase production in order to assess the role played by beta-lactamases in resistance to beta-lactam antibiotics. The data obtained showed that beta-lactamase production is undoubtedly a fundamental determinant for resistance. In fact, there was a significant correlation between the specific activity of the enzyme and the MIC of the strains considered. However, the role played by permeability barriers and/or other factors should be stressed, especially in determining resistance to cephalosporins. The validity of the nitrocefin test for detection of beta-lactamase production in Enterobacteriaeae from clinical isolates was also investigated
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
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