1,720,997 research outputs found
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
Molecular analysis of clinical isolates of Mycobacterium bovis recovered from humans in Italy
No full textIn order to achieve a better knowledge of Mycobacterium bovis epidemiology in Italy, 42 clinical isolates from humans were genotyped. Predominant molecular patterns were found in one cluster of 15 isolates sharing spoligotype (ST482), variable-number tandem repeat (VNTR), and IS6110-based restriction fragment length polymorphism (one 1.9-kb band) profiles and in two clusters of 6 and 3 Mycobacterium bovis BCG isolates differing by one VNTR character. The remaining 18 isolates yielded unique profiles. Our results confirm the potential utility of spoligotyping and VNTR typing as a major typing system of M. bovis isolates
Clonaggio molecolare e caratterizzazione immunologica preliminare della proteina PPE44 di Mycobacterium tuberculosis
No full textIl genoma di Mycobacterium tuberculosis codifica per 68 proteine ricche in glicina e asparagina caratterizzate da un dominio conservato N-terminale di circa 180 aminoacidi, comprendente il motivo aminoacidico prolina-prolina-acido glutamico (PPE) e da un segmento variabile C-terminale. Le proteine PPE sono antigenicamente polimorfiche e si ritiene che abbiano un significato immunologico nell'infezione tubercolare, probabilmente come fonte di variabilità antigenica e/o inibendo la processazione dell'antigene. Sulla base di precedenti studi in cui avevamo dimostrato che il gene Rv2770c di M. tuberculosis H37Rv, codificante per la proteina PPE44, è sottoespresso nel ceppo attenuato H37Ra, è stata intrapresa una ricerca volta a definire il ruolo della proteina PPE44 nell’infezione tubercolare.
A tale scopo, il gene Rv2770c di M. tuberculosis H37Rv, ottenuto mediante PCR con primers specifici fiancheggianti la regione codificante, è stato clonato in E. coli XL1Blue nel plasmide pQE-30 UA. Dopo sequenziamento nucleotidico per verificare il corretto orientamento dell'inserto, il DNA plasmidico ottenuto è stato impiegato per trasformare E. coli M15(pREP4); l'espressione della proteina PPPE44 ricombinante (rPPE44) è stata indotta mediante IPTG e verificata mediante analisi SDS-PAGE e immunoblotting con anticorpo anti-(His)5; la proteina rPPE44 è stata infine purificata per affinità con agarosio-acido nitrilotriacetico Ni2+.
Studi preliminari hanno dimostrato che la proteina rPPE44 induce proliferazione cellulare e produzione di interferon- (IFN-) in colture di linfociti di sangue periferico di individui tubercolino-positivi, analogamente al derivato proteico purificato della tubercolina (PPD). L’infezione sperimentale per via sottocutanea di topi BALB/c con Mycobacterium bovis BCG induce anticorpi IgG anti-rPPE44 e una debole risposta immune T-dipendente anti-rPPE44, rispetto a quella anti-PPD, valutata in vitro come produzione di IFN-in colture di splenociti e di cellule di linfonodi drenanti ed in vivo come incremento di spessore del cuscinetto plantare dopo challenge specifico intracutaneo.
Nel complesso, i dati immunologici preliminari indicano che la proteina PPE44 costituisce un nuovo antigene di M. tuberculosis espresso nel corso dell’infezione tubercolare, il cui ruolo merita di essere approfondito
Immunogenicity of mycobacterial PPE44 (Rv2770c) in Mycobacterium bovis BCG-infected mice
No full textThe PPE protein family of Mycobacterium tuberculosis includes 69 glycine-rich proteins with a conserved N-terminal domain. Their role in tuberculosis is unknown, but it has been speculated that they may have an important immunological significance. In this investigation, we evaluated the immunogenicity of ppe44 (Rv2770c) gene product in BALB/c mice infected subcutaneously or intravenously with Mycobacterium bovis BCG. Mice infected subcutaneously developed high titers of anti-PPE44 IgG1 antibodies while PPE44-specific IgG2a antibodies were absent at all tested times; PPE44-primed cells from draining lymph nodes and spleen produced low levels of IFN- and a moderate degree of delayed type hypersensitivity was observed following PPE44 intracutaneous challenge. In mice infected intravenously, anti-PPE44 IgG1 antibody response was markedly higher compared to the subcutaneous infection; anti-PPE44 IgG2a antibodies at titers approximately 0.5-2.0 log10 lower than IgG1 were detected. IFN- production in PPE44-stimulated spleen cell cultures was transient.
Our results indicate that PPE44 represents a novel mycobacterial antigen expressed during subcutaneous and intravenous infection by M. bovis BCG in BALB/c mice. Both infection models seem to polarize the immune response to PPE44 towards a Th2 phenotype, as testified by the IgG1 isotype predominant over the IgG2a, and by the low IFN-gamma and delayed type hypersensitivity responses
Polimorfismo ed espressione del gene ppe44 in isolati clinici di Mycobacterium tuberculosis
No full textLe proteine PPE di Mycobacterium tuberculosis, definite sulla base del motivo aminoacidico Pro-Pro-Glu, costituiscono una famiglia di 69 proteine polimorfiche ricche in glicina ritenute una probabile fonte di variabilità antigenica del bacillo tubercolare. Nel nostro laboratorio, nell’ambito di ricerche sul ruolo immunologico della proteina PPE44 nell’infezione tubercolare, è stato studiato l’eventuale polimorfismo e l’espressione del gene ppe44 in isolati clinici rappresentativi delle principali linee filogenetiche di M. tuberculosis. L’analisi PCR-RFLP mediante tre diversi enzimi di restrizione ha mostrato profili di digestione identici in tutti gli isolati; inoltre, la sequenza nucleotidica del gene ppe44 degli isolati non ha evidenziato mutazioni, ad eccezione di una sostituzione nucleotidica in posizione 581 (TTC→TCC, Phe→Ser) ritrovata unicamente negli isolati di genotipo Beijing. L’espressione di ppe44 negli isolati clinici, determinata mediante real-time RT-PCR quantitativa, normalizzata rispetto al gene di riferimento costitutivamente espresso sigA e confrontata con quella del ceppo di riferimento H37Rv, è risultata notevolmente variabile negli isolati clinici, rivelandosi paragonabile a quella di H37Rv in circa il 25% degli isolati, significativamente aumentata nel 60% degli isolati e diminuita nel rimanente 15%; gli isolati di genotipo Beijing hanno mostrato elevati livelli di espressione di ppe44. Tali risultati dimostrano quindi una sostanziale conservazione del gene ppe44 ed, al tempo stesso, una marcata variabilità dell’espressione di ppe44 tra gli isolati clinici. Per valutare se tale variabilità di espressione sia potenzialmente in grado di influenzare la risposta immunitaria dell’ospite, è stata determinata la risposta anticorpale anti-PPE44 in pazienti con tubercolosi in atto ed in soggetti sani con infezione tubercolare latente. E’ stata così dimostrata un’ampia variabilità nella risposta immunitaria verso PPE44 in pazienti con infezione tubercolare sia per quanto riguarda i titoli anticorpali, sia per quanto riguarda la proporzione dei soggetti rispondenti. Tali risultati suggeriscono che l’espressione differenziale dei geni ppe possa costituire una fonte di variabilità antigenica che può quindi avere implicazioni nella immunopatogenesi della tubercolosi
Hydroxamic Acid Derivatives: From Synthetic Strategies to Medicinal Chemistry Applications
Full text linkSince the approval of three hydroxamic acid-based HDAC inhibitors as anticancer drugs, such functional groups acquired even more notoriety in synthetic medicinal chemistry. The ability of hydroxamic acids (HAs) to chelate metal ions makes this moiety an attractive metal binding group - in particular, Fe(III) and Zn(II) - so that HA derivatives find wide applications as metalloenzymes inhibitors. In this minireview, we will discuss the most relevant features concerning hydroxamic acid derivatives. In a first instance, the physicochemical characteristics of HAs will be summarized; then, an exhaustive description of the most relevant methods for the introduction of such moiety into organic substrates and an overview of their uses in medicinal chemistry will be presented
Immune responses to protein PPE44 (Rv2770c) in mice infected with Mycobacterium bovis BCG
No full textBackground
The PPE protein family of Mycobacterium tuberculosis includes 69 glycine-rich proteins. Their role in tuberculosis is unknown, but it has been speculated that they may have an important immunological significance. In this investigation, the immunogenicity of the ppe44 (Rv2770c) gene product was evaluated in mice infected with Mycobacterium bovis BCG. Moreover, the protective efficacy of a DNA vaccine expressing ppe44 was evaluated in mice.
Methods
The gene ppe44 of M. tuberculosis H37Rv was cloned in E. coli and the purified recombinant protein (rPPE44) was used to evaluate antibody, cytokine and DTH responses in BALB/c mice infected with M. bovis BCG. The potential protective efficacy of PPE44 was evaluated in BALB/c and C57Bl/6 mice immunized intramuscularly with a DNA vaccine expressing ppe44 (ppe44-DNA) and challenged intravenously with M. bovis BCG.
Results
BALB/c mice infected subcutaneously developed high titers of anti-rPPE44 IgG1, but no IgG2a antibodies. Cultures of rPPE44-primed cells from draining lymph nodes and spleen produced low levels of IFN-; a moderate degree of DTH was observed following rPPE44 intracutaneous challenge. Similar results were obtained in mice infected intravenously.
BALB/c mice immunized with ppe44-DNA developed anti-rPPE44 IgG1 predominant over IgG2a antibodies; rPPE44-primed spleen cell cultures did not produce significant levels of IFN-. This regime of immunization conferred a moderate protection against an intravenous challenge with M. bovis BCG, as shown by the reduction of CFUs in the lungs compared to control mice immunized with the empty vector. C57Bl/6 mice immunized with ppe44-DNA developed comparable titers of anti-rPPE44 IgG1 and IgG2c antibodies; rPPE44-primed spleen cell cultures produced IFN-but no IL-4. After an intravenous challenge with M. bovis BCG, a one-log10 reduction of CFUs was detected in the lungs of ppe44-DNA immunized animals.
Conclusions
PPE44 represents a novel mycobacterial antigen expressed during infection by M. bovis BCG in mice. Both subcutaneous and intravenous infections seem to polarize the immune response to PPE44 towards a Th2 phenotype. Immunization of mice with ppe44-DNA confers a partial protection against an intravenous challenge with M. bovis BCG. The protective efficacy of PPE44 needs to be further evaluated by other experimental models aimed at enhancing the Th1-type immune responsiveness
Requirement of gene fadD33 for the growth of Mycobacterium tuberculosis in a hepatocyte cell line
No full textGene fadD33 of Mycobacterium tuberculosis, one of the 36 homologues of gene fadD of Escherichia coli identified in the M. tuberculosis genome, predictively encodes an acyl-CoA synthase, an enzyme involved in fatty acids metabolism. The gene is underexpressed in the attenuated strain M. tuberculosis H37Ra relative to virulent H37Rv and plays a role in M. tuberculosis virulence in BALB/c mice by supporting mycobacterial replication in the liver. In the present paper, we investigated the role of fadD33 expression in bacterial growth within the hepatocyte cell line HepG2, as well as in human monocyte-derived THP-1 cells and peripheral blood mononuclear cells. M. tuberculosis H37Rv proved able to grow within HepG2 cells, while the intracellular replication of M. tuberculosis H37Ra was markedly impaired; complementation of strain H37Ra with gene fadD33 restored its replication to the levels of H37Rv. Moreover, disruption of gene fadD33 by allelic exchange mutagenesis reduced the intracellular growth of M. tuberculosis H37Rv, and complementation of the fadD33-disrupted mutant with gene fadD33 restored bacterial replication. Conversely, fadD33 expression proved unable to influence M. tuberculosis growth in human phagocytes, as fadD33-disrupted M. tuberculosis H37Rv mutant, as well as fadD33-complemented M. tuberculosis H37Ra, grew within THP-1 cells and peripheral monocytes basically at the same rates as parent H37Rv and H37Ra strains. The results of these experiments indicate that gene fadD33 expression confers growth advantage to M. tuberculosis in immortalized hepatocytes, but not in macrophages, thus emphasizing the importance of fadD33 in liver-specific replication of M. tuberculosis
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