1,720,976 research outputs found
Advances in leishmaniasis: development of molecular diagnostic approaches and identification of new compounds against Leishmania (Leishmania) infantum
Full text linkLeishmaniases are a group of anthropo-zoonic parasitic diseases caused by a protozoan belonging
to Leishmania genus with a worldwide distribution that affects mainly the developing countries. The
parasite has different hosts such as humans, dogs, and wild animals. Despite the surveillance
programs introduced by the WHO, the disease still causes relevant problems in poor countries.
Moreover, the treatments available are few and present several limitations such as toxicity,
difficulty in administration, relapse, high production cost, and the appearance of resistant strains.
In this view, the aims of the thesis were the development of molecular assays mainly based on qPCR
and HRM analysis to differentiate the most common pathogenic species for humans and the
discovery of new classes of compounds more effective and safer against L. infantum. We established
a diagnostic algorithm involving 3 different SYBR green-based qPCR assays for the effective
discrimination among Viannia subgenus, L. mexicana complex and L. (L.) infantum, appliable on
clinical samples without the parasite isolation. On the other hand, we tested a library of 3,3’-
diindolylmethane (DIM) derivatives for their anti-leishmanial potential, first in terms of efficacy on
L. infantum promastigotes and then on intracellular amastigotes. The results allowed us to find new
promising classes of compounds never tested before with a good IC50 laying the bases for future
studies of optimization in term of pharmacokinetics, pharmacodynamics and bioavailability. Once
entered in the host macrophages, Leishmania promastigotes are able to subvert the innate immune
response and metabolic pathways of the host. The characterization of the molecular mechanisms
underlying Leishmania infection and the pathogen survival in host cells can contribute to identifying
new targets for therapeutic approaches. Since dogs represent one of the most important reservoirs
of infection for leishmaniasis, in the optic of a "one health" approach, we evaluated the gene
expression of some ER stress-related genes and miR-346 by qPCR in a canine macrophage cell line
(DH82) infected by Leishmania spp. and we compared the presence of the micro-RNA cfa-miR-346
in plasma of dogs non-infected and naturally infected with L. infantum. The results in DH82 cells
showed that cfa-mir-346 was induced post-infection with all Leishmania strain/isolates tested.
Moreover, the cfa-miR-346 expression analysis on dogs’ plasma revealed a significant upregulation
in infected dogs compared to non-infected dogs identifying the miRNA-346 as an infection marker
in dogs affected by leishmaniasis. In summary, this thesis illustrates our attempt to contribute to
the improvement of both diagnostics and therapeutics, in the context of a one health approach, to
reduce the burden of this complex and heterogeneous disease
Unveiling the Link Between NADPH Oxidase 2 Activation and Mitochondrial Superoxide Formation in Leukemic Cell Killing Induced by Arsenic Trioxide
Full text linkThis study focused on the interplay between NADPH oxidase 2 (NOX 2) activation and mitochondrial superoxide (mitoO2.-) formation induced by clinically relevant concentrations of arsenic trioxide (ATO; As2O3) in acute promyelocytic leukemia (APL) cells.
Carefully controlled inhibitor studies and small interfering RNA mediated downregulation of p47phox (a component of the NOX 2 complex) expression demonstrated that, in an APL cell line, ATO promotes upstream NOX 2 activation critically connected with the formation of mitoO2.- and with the ensuing mitochondrial permeability transition (MPT)-dependent apoptosis.
Instead, acute myeloid leukemia (AML) cell lines respond to ATO with low NOX 2 activation, resulting in a state that is non-permissive for mitoO2.- formation. Consistently, through rescue experiments, we demonstrate that pharmacological stimulation of NOX 2 overcomes resistance in these cells, thereby initiating the same cascade of downstream events observed in APL cells.
As a final note, several lines of evidence, including measurement of glutathione, catalase and glutathione peroxidase levels, indicated that the antioxidant machinery was similar in APL and AML cells. The results regarding nuclear factor erythroid 2 p45-related factor 2-dependent antioxidant responses were instead of more complex interpretation as NB4 cells appeared particularly responsive to ATO.
Our findings allow a novel interpretation of the interplay between NOX 2 activation and mitoO2.- formation induced by ATO, ultimately steering leukemic cells towards MPT-dependent apoptosis. These mechanistic insights provide a rationale for the disparate responses of APL and AML cells to ATO, offering potential avenues for the development of therapeutic intervention tailored to specific leukemia subtypes
The host micro-RNA cfa-miR-346 is induced in canine leishmaniasis
Full text linkBackground
Leishmaniases are a group of anthropo-zoonotic parasitic diseases caused by a protozoan of the Leishmania genus, affecting both humans and other vertebrates, including dogs. L. infantum is responsible for the visceral and occasionally cutaneous form of the disease in humans and canine leishmaniasis. Previously, we have shown that L. infantum induces a mild but significant increase in endoplasmic reticulum (ER) stress expression markers to promote parasites survival in human and murine infected macrophages. Moreover, we demonstrated that the miRNA hsa-miR-346, induced by the UPR-activated transcription factor sXBP1, was significantly upregulated in human macrophages infected with different L. infantum strains. However, the ER stress response in infected dogs, which represent an important reservoir for Leishmania parasite, was described once recently, whereas the miR-346 expression was not reported before. Therefore, this study aimed to investigate these pathways in the canine macrophage-like cell line DH82 infected by Leishmania spp. and to evaluate the presence of cfa-miR-346 in plasma of non-infected and infected dogs.
The DH82 cells were infected with L. infantum and L. braziliensis parasites and the expression of cfa-mir-346 and several ER stress markers was evaluated by quantitative PCR (qPCR) at different time points. Furthermore, the cfa-miR-346 was monitored in plasma collected from non-infected dogs (n = 11) and dogs naturally infected by L. infantum (n = 18).
Results
The results in DH82 cells showed that cfa-mir-346 was induced at both 24 h and 48 h post-infection with all Leishmania strains but not with tunicamycin, accounting for a mechanism of induction independent from sXBP1, unlike what was previously observed in human cell lines. Moreover, the cfa-miR-346 expression analysis on plasma revealed a significant increase in infected dogs compared to non-infected dogs.
Conclusions
Here for the first time, we report the upregulation of cfa-miR-346 induced by Leishmania infection in canine macrophage-like cells and plasma samples of naturally infected dogs. According to our results, the cfa-miR-346 appears to be linked to infection, and understanding its role and identifying its target genes could contribute to elucidate the mechanisms underlying the host–pathogen interaction in leishmaniasis
The use of conjunctival swabs in the diagnosis of human visceral leishmaniasis
No full textHuman visceral leishmaniasis (VL) is a severe disease whose diagnosis comprises immunological tests, microscopic biopsy examination, and biomolecular assays. In veterinary medicine, conjunctival swabs are widely used for detection of parasite DNA. Here, we describe the case of human VL in which conjunctival swabs were successfully used for Leishmania detection
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
ERO1α primes the ryanodine receptor to respond to arsenite with concentration dependent Ca2+ release sequentially triggering two different mechanisms of ROS formation
Full text link: A 6 h exposure of U937 cells to 2.5 μM arsenite stimulates low Ca2+ release from the inositol 1, 4, 5-triphosphate receptor (IP3R), causing a cascade of causally connected events, i.e., endoplasmic reticulum oxidoreductin-1α (ERO1α) expression, activation of the ryanodine receptor (RyR), mitochondrial Ca2+ accumulation, mitochondrial superoxide formation and further ERO1α expression. At greater arsenite concentrations, the release of the cation from the IP3R and the ensuing ERO1α expression remained unchanged but were nevertheless critical to sequentially promote concentration-dependent increases in Ca2+ release from the RyR, NADPH oxidase activation and a third mechanism of ERO1α expression which, in analogy to the one driven by mitochondrial superoxide, was also mediated by reactive oxygen species (ROS) and devoid of effects on Ca2+ homeostasis. Thus, concentration-independent stimulation of Ca2+ release from the IP3R is of pivotal importance for the effects of arsenite on Ca2+ homeostasis. It stimulates the expression of a fraction of ERO1α that primes the RyR to respond to the metalloid with concentration-dependent Ca2+-release, triggering the formation of superoxide in the mitochondrial respiratory chain and via NADPH oxidase activation. The resulting dose-dependent ROS formation was associated with a progressive increase in ERO1α expression, which however failed to affect Ca2+ homeostasis, thereby suggesting that ROS, unlike IP3R-dependent Ca2+ release, promote ERO1α expression in sites distal from the RyR
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
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