1,720,960 research outputs found
Il microRNA-101 regola la proteina precursore del peptide β-amiloide
Full text linkNella patogenesi della malattia di Alzheimer, il livello di espressione della proteina precursore del peptide β-amiloide (APP) riveste un ruolo determinante. E’ stato evidenziato che mutazioni che incrementano la sintesi proteica di APP, inclusa la duplicazione genica del locus di APP in alcune famiglie e nella trisomia del cromosoma 21, che contiene il gene APP, sono sufficienti per indurre lo sviluppo della patologia in forma precoce. Per questo motivo, la regolazione del gene APP è stata oggetto di intensi studi riguardanti sia la caratterizzazione del promotore, che le regioni 5’ e 3’ non tradotte dell’RNA messaggero. Negli ultimi anni, il meccanismo di regolazione post-trascrizionale dell’espressione genica mediato dai microRNA è stato estesamente indagato in diversi meccanismi biologici e in vari tipi cellulari. I microRNA modulano finemente la traduzione di proteine necessarie alla risposta a stimoli di origine extracellulare, ed in altri casi definiscono spazialmente e temporalmente i profili di espressione di geni coinvolti nello sviluppo e differenziamento.
Lo svolgimento di questa tesi sperimentale ha trovato il suo avvio nella domanda se il sistema dei microRNA fosse coinvolto in maniera significativa nella regolazione dell’espressione dell’APP.
Tramite RNAi, è stata silenziato il gene Argonauta 2, componente fondamentale del complesso ribonucleoproteico che media l’azione dei microRNA, ed è stato osservato un aumento della proteina APP. Mediante analisi bioinformatica sono stati individuati i possibili microRNA interagenti con APP ed è stato scelto il miR-101, arricchito nel sistema nervoso.
Tramite analisi dei profili di espressione in ippocampo di ratto, tra gli 8 giorni e i 6 mesi di età, è stata osservata una correlazione inversa tra i livelli di miR-101, che aumenta, e APP, che diminuisce nel corso del tempo.
Utilizzando un costrutto reporter, è stata dimostrata la capacità del miR-101 di inibire la traduzione di APP attraverso l’interazione diretta con il 3’UTR del messaggero.
Bloccando l’azione del miR-101 in colture primarie ippocampali, è stato osservato un significativo aumento della proteina APP endogena, confermando l’azione regolatoria del microRNA nel contesto neuronale fisiologico, mentre la over-espressione del miR-101 si è rivelata efficace nell’indurre una repressione a livello post-trascrizionale dell’APP.
E’ stato inoltre osservato che la stimolazione di neuroni ippocampali con Interleuchina-1β, principale mediatore della neuroinfiammazione e fattore di rischio per AD, induce una modulazione coordinata nel tempo di APP e del miR-101.
I dati ottenuti dimostrano quindi l’esistenza di un’attività repressiva del miR-101 sull’APP in condizioni fisiologiche, mentre la perturbazione di tale regolazione è sufficiente ad indurre un aumento della proteina APP, condizione associata alla patologia di Alzheimer.
Considerando studi recenti, in cui il miR-101 è stato visto down-regolato in cervelli di casi sporadici di malattia di Alzheimer, e i dati qui ottenuti, miR-101 può essere visto come un regolatore con attività protettiva verso una eccessiva produzione del precursore del peptide β-amiloide.
La caratterizzazione della via di trasduzione del segnale, neuroinfiammatorio, che coinvolge il miR-101, e la sua possibile associazione con la patologia di Alzheimer potrebbero aprire nuovi scenari nella eziopatogenesi di questa malattia neurodegenerativa.In the pathogenesis of Alzheimer's disease, the expression level of the β-amyloid precursor protein (APP) plays a crucial role. It has been shown that mutations which increase APP protein synthesis, including the duplication of the locus of APP gene in certain families and trisomy of chromosome 21 (containing the APP gene), are sufficient to induce the early form of pathology. Therefore APP gene regulation has been extensively studied and both the promoter and 5’ and 3’ untranslated regions of mRNA have been charachterised. In recent years, the post-transcriptional mechanism of gene expression mediated by microRNAs has been discovered and investigated in several biological mechanisms and cell types. MicroRNAs have been shown to finely modulate the translation of proteins needed for the response to extracellular stimuli, and to define the spatial and temporal expression profiles of genes involved in neuronal development and differentiation.
This experimental thesis focused on the question whether microRNAs are significantly involved in APP regulation.
Through RNAi , Argonauta-2 gene, a key component of the ribonucleoprotein complex mediating the action of microRNAs, was silenced and APP protein increase was observed. Through bioinformatic analysis, microRNAs potentially interacting with APP have been identified and miR-101, which is enriched in the nervous system, was further investigated.
Through expression analysis in rat hippocampus, from 8 days up to 6 months of age, it was observed an inverse correlation between miR-101 levels, which increase, and APP expression, which decreases over time.
Using a reporter construct, the ability of miR-101 to inhibit the translation of APP through direct interaction with the messenger 3’UTR was demonstrated.
Through inhibition of miR-101 in hippocampal primary cultures, a significant increase of endogenous APP protein was observed, confirming the miRNA regulatory function in the neuronal context. Instead miR-101 over-expression was effective in inducing APP repression at post-transcriptional level.
It was also observed that stimulation of hippocampal neurons with IL-1, the first player of neuroinflammation and risk factor for Alzheimers Disease, induces coordinated modulation of APP and miR-101.
These data demonstrate the repressive effect of miR-101 on APP under physiological conditions, while the alteration of this regulation is sufficient to induce an increase of APP protein, a condition which is associated to familial Alzheimer’s disease.
In view of previous studies, in which miR-101 was shown to be down-regulated in the brains of sporadic cases of Alzheimer's disease, and of data obtained in this work, miR-101 may be a protective regulator of excessive production of β-amyloid precursor protein.
The characterization of the signal transduction pathway activated by neuroinflammation, involving miR-101, and the relationship between this pathway and Alzheimer's disease might open a new perspective on the pathogenesis of this neurodegenerative disease
MicroRNA-101 regulates amyloid precursor protein expression in hippocampal neurons.
No full textThe amyloid precursor protein (APP) and its proteolytic
product amyloid beta (A) are associated with both familial and
sporadic forms of Alzheimer disease (AD). Aberrant expression
and function of microRNAs has been observed in AD. Here, we
show that in rat hippocampal neurons cultured in vitro, the
down-regulation of Argonaute-2, a key component of the
RNA-induced silencing complex, produced an increase in
APP levels. Using site-directed mutagenesis, a microRNA
responsive element (RE) for miR-101 was identified in the
3-untranslated region (UTR) of APP. The inhibition of
endogenous miR-101 increased APP levels, whereas lentiviral-
mediated miR-101 overexpression significantly reduced
APPandA load in hippocampal neurons. In addition, miR-101
contributed to the regulation of APP in response to the proinflammatory
cytokine interleukin-1 (IL-l). Thus, miR-101 is a
negative regulator of APP expression and affects the accumulation
of A, suggesting a possible role for miR-101 in neuropathological
condition
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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