1,721,021 research outputs found
Strategies for the adult haemoglobin (HbA) production in β0-thalassemia patients
No full textBackground: Nonsense mutations, giving rise to UAA, UGA, UAG stop
codons within the coding region of mRNAs, promote premature translational
termination and are the leading cause of about 30% of inherited diseases,
including cystic fibrosis, Duchenne muscular dystrophy, thalassemia.
Currently, there are two approaches to directly overcome diseases caused by
nonsense mutations: gene therapy, meaning introduction of an exogenous gene,
and translational read-through induced by aminoglycosides, which decrease the
accuracy of translation elongation and reduce the efficacy of the translation
termination machinery. Interestingly, recent papers have described drugs designed
and produced for suppressing premature translational termination, inducing a
ribosomal read-through of premature but not normal termination codons. On the
other hand, in recent years, many investigators have been studying the
development of safe lentiviral vectors to avoid the side effects as activation of
oncogenes and transcription silencing.
Aim: Our purpose was to verify the effects and clinical utility in b0-
thalassemia of translational read-through and gene therapy.
Methods: First, we started the development of a cellular model of the b039-
thalassemia mutation that could be used for the screening of high numbers of
aminoglycosides and analogous molecules. We produced two lentiviral vectors
containing the bwt- or b039-thalassemia globin gene under a minimal LCR control
region and used such constructs for the transduction of K562 cells, subsequently
subcloned, with the purpose to obtain several K562 clones with different copynumber
of the integrated constructs. These clones were then treated with geneticin
(G418) and other aminoglycosides and the production of β-globin was analysed by
FACS analysis.
Secondly, we screened several thalassemia patients and isolated erythroid
progenitors from such individuals resulted homozygous for the b039 mutation.
Then, we treated the cells with geneticin and analysed the production of b-globin
and adult haemoglobin (HbA) by FACS and HPLC analysis, respectively.
Finally, we subjected the b039 erythroid precursor cells to gene therapy,
through the use of the lentiviral vector expressing the βwt-globin mRNA, with the
aim to verify the increase of HbA through HPLC analysis. Moreover, by treating
the transduced cells with mithramycin we wanted to verify the combined effects of
gene therapy and fetal haemoglobin (HbF) induction.
Main results: We obtained and characterized six clones carrying the b039-
globin gene and seven clones carrying the bwt-globin gene, to be used as a
control. We then chose two clones, a bwt and a b039, showing similar content of
mRNA and used them to test various aminoglycosides to verify their read-through
activity. Geneticin (G418) and gentamicin showed the highest capacity to readthrough
of nonsense mutation, although the effect of G418 was found to be higher
than that displayed by gentamicin. A significant increase in β-globin containing
cells was also detected when b039 progenitor cells were treated with G418. This
last result was confirmed by HPLC analysis, which showed an increase in the
relative concentration of HbA compared to total Hbs.
Finally, we obtained a high increase in the proportion of HbA when the same
progenitor cells were subjected to gene therapy, through transduction with the
lentiviral vector containing the bwt-globin gene, and a clear increment of HbF was
detected after treatment with mithramycin.
Conclusion: Both the therapeutic approaches for the cure of β0-thalassemias
analysed in this work, namely translational read-through and gene therapy, while
still presenting many disadvantages, including toxicity of aminoglycosides and the
uncertainty of the effects of lentiviral vectors on endogenous genes, can be
considered techniques with a high curative potential. Naturally, in the case of
translational read-through is hoped the identification of new compounds with a therapeutic effect similar to but greater than that of aminoglycosides, with less
toxicity and oral bioavailability, while in the case of gene therapy, further
investigations should be made to eliminate its well known disadvantages,
primarily including the possible activation of oncogenes
Therapeutic molecules for the development of a read-through approach for diseases caused by nonsense mutations
No full textNonsense mutations lead to premature translational termination and mRNA destabilization through nonsense-mediated RNA decay. These mutations rise to premature translation termination codons (PTTCs) within the coding region of mRNAs and are the cause of approximately 30% of inherited diseases, including thalassemia and cystic fibrosis. Premature arrest of translation may involve the synthesis of truncated abnormal proteins that can be toxic to target cells through dominant negative or gain-of-function effects. The functional consequences of nonsense mutations are further affected by the nonsense-mediated RNA decay, a cellular mechanism aimed to detect and degrade PTTCs containing mRNAs. In the last few years, it has been demonstrated that drugs (such as aminoglycoside antibiotics) can be designed and produced to suppress premature translation termination, inducing a ribosomal read-through of premature, but not normal termination codons. Moreover, the treatments with aminoglycosides may restore the loss function in patients with nonsense mutations and have introduced new hopes for the development of a pharmacologic approach of these diseases
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
Screening Readthrough Compounds to Suppress Nonsense Mutations: Possible Application to β-Thalassemia
Full text linkSeveral types of thalassemia (including beta(0)39-thalassemia) are caused by nonsense mutations in genes controlling globin production, leading to premature translation termination and mRNA destabilization mediated by the nonsense mediated mRNA decay. Drugs (for instance, aminoglycosides) can be designed to suppress premature translation termination by inducing readthrough (or nonsense suppression) at the premature termination codon. These findings have introduced new hopes for the development of a pharmacologic approach to cure this genetic disease. In the present review, we first summarize the principle and current status of the chemical relief for the expression of functional proteins from genes otherwise unfruitful for the presence of nonsense mutations. Second, we compare data available on readthrough molecules for beta(0)-thalassemia. The examples reported in the review strongly suggest that ribosomal readthrough should be considered as a therapeutic approach for the treatment of beta(0)-thalassemia caused by nonsense mutations. Concluding, the discovery of molecules, exhibiting the property of inducing beta-globin, such as readthrough compounds, is of great interest and represents a hope for several patients, whose survival will depend on the possible use of drugs rendering blood transfusion and chelation therapy unnecessary
Acute gastrointestinal bleeding following aortic valve replacement in a patient with Heyde's sindrome. Case report.
No full textA 58-year old man was admitted to the hospital because of melena. He had a 1-year history of mechanical aortic valve replacement and coronary stent placement because of myocardial infarction and he was taking warfarin and clopidogrel. Esophagogastroduodenoscopy and colonoscopy were negative for bleeding. Capsule endoscopy showed bleeding diffuse angiodysplasia of the small bowel. The patient was treated with octreotide 20 mg, at monthly interval. After 25 months there had been no recurrence of gastrointestinal bleeding. The case suggests that mechanical valve replacement may not prevent gastrointestinal bleeding in Heyde syndrome and that octreotide treatment should be considered in these cases
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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