1,721,183 research outputs found
Purpurin suppresses Candida albicans biofilm formation and hyphal development
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A link between virulence and homeostatic responses to hypoxia during infection by the human fungal pathogen Cryptococcus neoformans.
Get PDFFungal pathogens of humans require molecular oxygen for several essential biochemical reactions, yet virtually nothing is known about how they adapt to the relatively hypoxic environment of infected tissues. We isolated mutants defective in growth under hypoxic conditions, but normal for growth in normoxic conditions, in Cryptococcus neoformans, the most common cause of fungal meningitis. Two regulatory pathways were identified: one homologous to the mammalian sterol-response element binding protein (SREBP) cholesterol biosynthesis regulatory pathway, and the other a two-component-like pathway involving a fungal-specific hybrid histidine kinase family member, Tco1. We show that cleavage of the SREBP precursor homolog Sre1-which is predicted to release its DNA-binding domain from the membrane-occurs in response to hypoxia, and that Sre1 is required for hypoxic induction of genes encoding for oxygen-dependent enzymes involved in ergosterol synthesis. Importantly, mutants in either the SREBP pathway or the Tco1 pathway display defects in their ability to proliferate in host tissues and to cause disease in infected mice, linking for the first time to our knowledge hypoxic adaptation and pathogenesis by a eukaryotic aerobe. SREBP pathway mutants were found to be a hundred times more sensitive than wild-type to fluconazole, a widely used antifungal agent that inhibits ergosterol synthesis, suggesting that inhibitors of SREBP processing could substantially enhance the potency of current therapies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
The Aspergillus nidulans transcription factor SclB governs the transition from vegetative to asexual development
No full textABSTRACT Asexual reproduction in filamentous fungi is a common, efficient, and fast differentiation process for producing large numbers of asexual spores (conidia), which can be distributed through the air to colonize new environments. The whole process is tightly controlled by specific regulatory proteins. Among the major regulators is the zinc cluster protein of SclB (sclerotia-like B), known to influence various aspects of asexual growth and secondary metabolism in Aspergillus nidulans as well as other filamentous fungi. Two different growth conditions of A. nidulans were compared to obtain a mechanistic overview of the role of SclB, mainly during the transition of the fungus from vegetative to asexual growth. Chromatin immunoprecipitation (IP) was coupled with next-generation sequencing (ChIP-seq) and combined with transcriptomic analyses (RNA-seq). SclB coordinates this developmental shift mainly by controlling the expression of genes encoding a few, however, prominent regulators of conidiation. These include the transcription factors BrlA, VelB, and SclB and the pheromone oxygenase PpoC. Association of SclB to promoter regions requires the newly identified putative SclB response element with a nine-base-pair DNA motif. Scl2 is the corresponding protein in the fungal plant pathogen Verticillium dahliae and partially complements the A. nidulans Δ sclB asexual deficiency. This supports a partial functional complementation of this regulator among different fungal species. In summary, SclB coordinates the transition from vegetative growth to asexual reproduction in A. nidulans through in vivo transcriptional control over genes coding for established players of conidia formation. IMPORTANCE Fungi constantly adapt to environmental changes in their various habitats. Asexual spore formation allows for quickly leaving an unfriendly habitat through dispersal into the air. The asexual developmental program of fungi enables the production of a large number of spores in a short period of time and in an energetically efficient manner. The SclB transcription factor is a key regulator of asexual growth and secondary metabolism in numerous fungal species. The mechanism through which SclB orchestrates the transition of the filamentous fungus Aspergillus nidulans from vegetative to asexual growth was revealed. This regulator directly in vivo controls itself as well as the expression of master genes for the asexual program, such as brlA for transcriptional control or ppoC for pheromone production. This study enhances the molecular understanding of how fungal asexual differentiation is initiated and coordinated, which supports the development of better strategies to control fungal pathogens, improving human health, safety, and crop management.Fungi constantly adapt to environmental changes in their various habitats. Asexual spore formation allows for quickly leaving an unfriendly habitat through dispersal into the air. The asexual developmental program of fungi enables the production of a large number of spores in a short period of time and in an energetically efficient manner. The SclB transcription factor is a key regulator of asexual growth and secondary metabolism in numerous fungal species. The mechanism through which SclB orchestrates the transition of the filamentous fungus Aspergillus nidulans from vegetative to asexual growth was revealed. This regulator directly in vivo controls itself as well as the expression of master genes for the asexual program, such as brlA for transcriptional control or ppoC for pheromone production. This study enhances the molecular understanding of how fungal asexual differentiation is initiated and coordinated, which supports the development of better strategies to control fungal pathogens, improving human health, safety, and crop management.ABSTRACT Asexual reproduction in filamentous fungi is a common, efficient, and fast differentiation process for producing large numbers of asexual spores (conidia), which can be distributed through the air to colonize new environments. The whole process is tightly controlled by specific regulatory proteins. Among the major regulators is the zinc cluster protein of SclB (sclerotia-like B), known to influence various aspects of asexual growth and secondary metabolism in Aspergillus nidulans as well as other filamentous fungi. Two different growth conditions of A. nidulans were compared to obtain a mechanistic overview of the role of SclB, mainly during the transition of the fungus from vegetative to asexual growth. Chromatin immunoprecipitation (IP) was coupled with next-generation sequencing (ChIP-seq) and combined with transcriptomic analyses (RNA-seq). SclB coordinates this developmental shift mainly by controlling the expression of genes encoding a few, however, prominent regulators of conidiation. These include the transcription factors BrlA, VelB, and SclB and the pheromone oxygenase PpoC. Association of SclB to promoter regions requires the newly identified putative SclB response element with a nine-base-pair DNA motif. Scl2 is the corresponding protein in the fungal plant pathogen Verticillium dahliae and partially complements the A. nidulans Δ sclB asexual deficiency. This supports a partial functional complementation of this regulator among different fungal species. In summary, SclB coordinates the transition from vegetative growth to asexual reproduction in A. nidulans through in vivo transcriptional control over genes coding for established players of conidia formation. IMPORTANCE Fungi constantly adapt to environmental changes in their various habitats. Asexual spore formation allows for quickly leaving an unfriendly habitat through dispersal into the air. The asexual developmental program of fungi enables the production of a large number of spores in a short period of time and in an energetically efficient manner. The SclB transcription factor is a key regulator of asexual growth and secondary metabolism in numerous fungal species. The mechanism through which SclB orchestrates the transition of the filamentous fungus Aspergillus nidulans from vegetative to asexual growth was revealed. This regulator directly in vivo controls itself as well as the expression of master genes for the asexual program, such as brlA for transcriptional control or ppoC for pheromone production. This study enhances the molecular understanding of how fungal asexual differentiation is initiated and coordinated, which supports the development of better strategies to control fungal pathogens, improving human health, safety, and crop management.Fungi constantly adapt to environmental changes in their various habitats. Asexual spore formation allows for quickly leaving an unfriendly habitat through dispersal into the air. The asexual developmental program of fungi enables the production of a large number of spores in a short period of time and in an energetically efficient manner. The SclB transcription factor is a key regulator of asexual growth and secondary metabolism in numerous fungal species. The mechanism through which SclB orchestrates the transition of the filamentous fungus Aspergillus nidulans from vegetative to asexual growth was revealed. This regulator directly in vivo controls itself as well as the expression of master genes for the asexual program, such as brlA for transcriptional control or ppoC for pheromone production. This study enhances the molecular understanding of how fungal asexual differentiation is initiated and coordinated, which supports the development of better strategies to control fungal pathogens, improving human health, safety, and crop management.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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