1,721,070 research outputs found
Carbon nanotubes on Jurkat cells: effects on cell viability and plasma membrane potential
No full textCarbon nanotubes (CNT) are one of the most novel attractive materials in nanotechnology for their potential multiple applications, including in the biomedical fields. The biocompatibility and toxicity of these novel nanomaterials are still largely unknown and a systematic study on biological interference is essential. We present a toxicological assessment of different types of CNT on the human tumor lymphocytic Jurkat cells. The carbon nanomaterials examined differ in preparation, size, contaminants and morphology: (1) CNT composed of MWCNT+SWCNT, with no metal contaminants; (2) MWCNT and (3) SWCNT, both with metal contaminants; (4) carbon black as control. The results indicate that CNT exert a dose- and time-dependent cytotoxic effect on Jurkat cells, inducing apoptotic cell death, accelerating the transition to secondary necrosis and increasing the extent of apoptosis induced by damaging agents; interestingly, CNT induce a plasma membrane hyperpolarization. These alterations are produced by all types of CNT, but contaminants and/or the size modulate the extent of such effects. Thus CNT deeply affect cell behavior, suggesting that they might play a role in inflammation, and recommending greater attention in terms of evaluation of exposure ris
Novel pathways induced by melatonin on leukocytes: possible pharmacological and inflammatory perspectives
Full text linkLa melatonina, oltre ad essere un regolatore dei ritmi circadiani, è stato recentemente dimostrato essere un modulatore del sistema immunitario attraverso il controllo del comportamento dei leucociti, i quali sono infatti in grado di sintetizzare la melatonina e possiedono specifici recettori di membrana (MT1 e MT2) ad alta affinità (1nM). L’abilità della melatonina di contrastare l’apoptosi sta ricevendo un grande interesse, un effetto ben accetto, nonostante il suo meccanismo sia ancora abbastanza controverso. In questo studio analizziamo il meccanismo coinvolto nell’effetto anti-apoptotico della melatonina in leucociti normali e tumorali. Abbiamo visto che questo effetto è dovuto a due differenti meccanismi cooperanti i quali coinvolgono due target primari con cui la melatonina interagisce; i recettori MT1/MT2 e la calmodulina, un noto target della melatonina a bassa affinità (63 uM). L’interazione con il recettore ed il legame alla calmodulina da origine a due pathways di trasduzione del segnale indipendenti, che consisono da una parte in una trasduzione del segnale canonica (convolgendo le proteine G e la fosfolipasi C), e dall’altra nell’attivazione della 5-lipossigenasi (5-LOX) tramite calmodulina /fosfolipasi A2 (un noto interattore della calmodulina) che termina con la produzione dei 5-HETE. Questi due pathways convergono nell’effetto anti-apoptotico di melatonina a livello mitocondriale, prevenendo l’attivazione di Bax, la chiave che innesca il pathway apoptotico intrinseco. La novità di questi risultati è che Bax è mantenuto nel mitocondrio in una stato anti-apoptotico. Infatti, la melatonina causa la translocazione di Bcl-2 al mitocondrio, dove si lega direttamente a Bax, inibendo la sua attivazione/dimerizzazione. L’effetto anti-apoptotico è completamente abrogato se uno o l’altro pathway viene inibito. La necessità del legame a bassa affinità con la calmodulina, spiega la necessità di alte dosi di melatonina (>100uM). Il coinvolgimento della 5-LOX nell’effetto anti-apoptotico della melatonina è particolarmente interessante dal momento che la necessità di un enzima chiave della risposta infiammatoria può fare nuova luce sul ruolo che la melatonina gioca nella regolazione della risposta immunitaria. Inoltre, l’attivazione della LOX implica uno sprigionarsi di radicali liberi che immediatamente (<1min) e fortemente (fino a 15 volte) segue alla somministrazione di melatonina, raggiungendo un picco a 2 ore per tornare a valori di controllo a 6 ore. Questo è un effetto biologico pro-ossidante che co-esiste e contrasta con la nota abilità della melatonina di radical scavanger.Melatonin, in addition to its main role as regulator of circadian rhythms, has recently been shown to modulate immune functions by controlling the behaviour of leukocytes, which are indeed able to synthesize melatonin and possess the specific high affinity (1nM) plasma membrane receptors (MT1 and MT2). Great interest is receiving the ability of melatonin to contrast apoptosis, a well accepted fact whose mechanisms however are still quite controversial. In this study, we analyze the mechanisms involved in the anti-apoptotic effect of melatonin in normal and tumor leukocytes. We have shown that this effect is due to two different, cooperating mechanisms, involving two primary targets melatonin directly interacts with, i.e., MT1/MT2 receptors; and calmodulin, a known melatonin low affinity (63uM) target. Receptor engagement and calmodulin binding give rise to two independent signal transduction pathways, consisting of a canonical MT1/MT2 receptor mediated signal transduction (involving G protein and phospholipase C) on the one side, and calmodulin/phospholipase A2 (a known calmodulin interactor)/5-lipoxygenase (LOX) activation culminating in 5-HETE production, on the other. These pathways converge into melatonin anti-apoptotic effect at the mitochondrial level, preventing the activation of Bax, the key trigger of the intrinsic apoptotic pathway. The novelty of this finding is that Bax is maintained within mitochondria in an anti-apoptotic state. Indeed, melatonin causes the translocation of Bcl-2 to mitochondria, which directly binds to Bax inhibiting its activation/dimerization. The anti-apoptotic effect is completely abrogated if one or the other pathway is inhibited. The necessity of the low affinity calmodulin binding explains the requirement of high melatonin doses (>100uM). The involvement of 5-LOX in the anti-apoptotic effect of melatonin is particularly intriguing since, the recruitment of a key enzyme of the inflammatory response may shed new lights on the role melatonin plays in the regulation of the immune response. Moreover, LOX activation implies a burst of free radicals that immediately (<1min) and strongly (up to 15folds) follows melatonin administration, peaking at 2hrs to go back to normal values at 6hrs. This is a biological pro-oxidant effect that co-exists with, and contrasts, the well known chemical radical scavenging ability of the melatonin molecule
Pathways of survival to oxidative stress: competition between Bcl-2 and Bax and role of NF-kappaB
No full textButhionine Sulfoximine (BSO) is a well-known inhibitor of glutathione synthesis, producing slow glutathione depletion and oxidative stress; some “responder” cells avoid BSO-induced death by trans-activating the pro-survival protein Bcl-2. Here we show that BSO activates a non-canonical, IκB- and p65-independent NFκB pathway, via a multi-step process leading to the up-regulation of Bcl-2. The slow BSO-induced GSH depletion allows separating two redox-related phases, namely, early thiol disequilibrium, and late frank oxidative stress; each phase contributes to the progressive activation of a p50-p50 homo-dimer. The early phase, coinciding with substantial thiol depletion, produces a cytosolic preparative complex, consisting of p50 and its inter-actor Bcl-3 linked by inter-protein disulfide bridges. The late phase, coinciding with ROS production, is responsible, probably via p38 activation, of nuclear targeting of the complex, and trans-activation of Bcl-2
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
Calcium alterations in apoptotic and survival pathways
No full textNumerosi studi hanno inizialmente descritto alterazioni del calcio (Ca2+), in termini di un aumento di Ca2+ citosolico, in apoptosi. Ciò ha portato alla opinione diffusa che una deregolazione dell’omeostasi del Ca2+ sia un evento richiesto per l’avvio dell’apoptosi. La recente disponibilità di sonde fluorescenti permeabili per analizzare i parametri di Ca2+ intracellulare insieme con il forte sviluppo di strumenti per le misure del Ca2+ stanno evidenziando che i meccanismi alla base della segnalazione intracellulare apoptotica sono molto più sofisticati di quanto creduto in precedenza e altre più sottili correlazioni tra il metabolismo del Ca2+ e la segnalazione apoptotica cominciano ad apparire. Così, il paradigma che l’apoptosi richieda un aumento di Ca2+ citosolico è attualmente messo in discussione dall’osservazione che un aumento di Ca2+ citosolico può paradossalmente esercitare sia un effetto pro-apoptotico che anti-apoptotico. Nonostante numerosi studi riguardanti il ruolo del Ca2+ nei fenomeni di apoptosi/sopravvivenza, ancora oggi resta da spiegare perché le alterazioni del Ca2+ possano svolgere ruoli così diversi in differenti sistemi cellulari e soprattutto il ruolo effettivo del Ca2+ nell’apoptosi/sopravvivenza è ancora elusivo.
In questa tesi, ho analizzato il ruolo del Ca2+ nei fenomeni di apoptosi/sopravvivenza, applicando differenti approcci (per es., mettendo a punto una nuova metodologia che permette l’analisi a livello di singola cellula di parametri statici e dinamici del Ca2+ in cellule indotte in apoptosi; perturbando, l’omeostasi del Ca2+ con diversi agenti chimici e fisici prima di indurre l’apoptosi). Attraverso questi approcci, ho identificato un numero di fasi progressive, temporalmente definite, caratterizzate da cambiamenti nei parametri del Ca2+ dopo l’induzione dell’apoptosi, sia in cellule pre-apoptotiche che francamente apoptotiche, indicando così che molteplici tipi di alterazioni del Ca2+ con differenti significati avvengono in apoptosi. Inoltre ho delineato l’esistenza di differenti pathway pro-sopravvivenza (che ho chiamato, rispettivamente, pathway di difesa cellulare e pathway di sopravvivenza) attuati in risposta a differenti stress e coinvolgenti il Ca2+ in modo opposto. I dati qui riportati sono consistenti con un ruolo dualistico del Ca2+ sulla sopravvivenza cellulare dipendente dal danno subito dalle cellule. Questo è in linea con emergenti evidenze che il Ca2+ possa svolgere un ruolo pro-apoptotico e anti-apoptotico. Pertanto, i miei dati potrebbero fornire una possibile spiegazione alle apparenti incongruenze di molti studi che descrivono le alterazioni del Ca2+ in apoptosi, indicando così che molteplici tipi di alterazioni di Ca2+ con differenti significati possono avvenire sia nei fenomeni di apoptosi che di sopravvivenza.Many earlier studies have described Ca2+ alterations in apoptosis in terms of cytosolic Ca2+ elevation, thus concluding that apoptosis may be triggered by a deregulation of Ca2+ homeostasis. However, the recent availability of fluorescent cell-permeant Ca2+ probes together with the strong development of Ca2+ measurements instruments are evidencing that apoptotic signalling mechanisms are more sophisticated that previously believed, and other, more subtle correlations between Ca2+ metabolism and apoptotic signalling begin to appear. Thus, the paradigm that apoptosis required an elevation of cytosolic Ca2+ is currently shaken by the finding that cytosolic Ca2+ elevation during apoptosis can paradoxically exert either a pro-apoptotic or an anti-apoptotic effect. However, in spite of many current studies concerning the role of Ca2+ in apoptosis/survival, it remains to be explained why Ca2+ alterations play different roles in the apoptosis of different cell systems, and overall the effective role of Ca2+ in apoptosis/survival is still elusive.
In this thesis, we have analysed the role of Ca2+ in apoptosis/survival, by applying different approaches (i.e., by setting up a novel method that allows the analysis at the single cell level of static as well as dynamic Ca2+ parameters in apoptosing cell; by perturbing Ca2+ homeostasis with different chemical and physical agents before inducing apoptosis). Through these approaches, we have identified a number of progressive, temporally defined phases, characterized by changes in Ca2+ parameters after the induction of apoptosis, among either pre-apoptotic or frankly apoptotic cells, thus indicating that multiple types of Ca2+ alterations with different meanings occur in apoptosis. Moreover, we have delineated the existence of different pro-survival pathways (namely cell defence pathway or pro-survival pathway) actuated in response to different stress and involving Ca2+ in opposite way. The data here presented are consistent with a dualistic effect of Ca2+ on cell survival depending on the damage suffered by cells. This is in line with emerging evidence that Ca2+ may play a pro-apoptotic and anti-apoptotic role. Thus, our data might account for the apparent incongruencies of many studies dealing with the study of Ca2+ alterations in apoptosis, thus indicating that multiple types of Ca2+ alterations with different meanings may occur in both apoptosis and survival
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
Biological effects of cerium oxide nanoparticles on leucocyte cell lines
No full textLa terapia antiossidante rappresenta una nuova frontiera per prevenire e curare una serie impressionante di gravi malattie umane, e la ricerca di farmaci antiossidanti adeguata è in aumento. Le nanoparticelle di ossido di cerio (nanoceria) sono considerate redox-attive perchè presentano la coesistenza di due stati di ossidazione, Ce3 + e Ce4+, e i difetti Ce3+, compensati dalle vacanze di ossigeno, sono più abbondanti in superficie. La nanoceria esercita eccezionali effetti antiossidanti in vivo, poichè agisce come un antisenescenza e anti-infiammatorio ben tollerato, e può essere considerata potenzialmente uno strumento terapeutico innovativo. Tuttavia, il meccanismo antiossidante che genera questo effetto biologico è ancora poco chiaro. In questa tesi di dottorato, è stata effettuata una analisi su due linee cellulari di leucociti, indotti in apoptosi attraverso meccanismi redox-dipendenti o indipendenti; questo studio ha consentito di dimostrare una relazione diretta di causa-effetto tra l’effetto antiossidante e prosopravvivenza della nanoceria. La nanoceria drogata con samario, che diminuisce la quantità di Ce3+ e aumenta il contenuto di vacanze dell’ossigeno, riduce questi effetti, a dimostrazione che le reazioni redox tra Ce3+ / Ce4+ sono responsabili dell'eccezionale proprietà in vivo della nanoceria.Antioxidant therapy is the novel frontier to prevent and treat an impressive series of severe human diseases, and the search for adequate antioxidant drugs is fervent. Cerium oxide nanoparticles (nanoceria) are redox-active owing to the co-existence of Ce3+ and Ce4+ oxidation states and to the fact that Ce3+ defects, and the compensating oxygen vacancies, are more abundant at the surface. Nanoceria exert outstanding antioxidant effects in vivo acting as well tolerated anti-age and anti-inflammatory agents, potentially being innovative therapeutic tools. However, the biological antioxidant mechanisms are still unclear. Here, the analysis on two leukocyte cell lines undergoing apoptosis via redox-dependent or independent mechanisms, allowed demonstrating a direct cause-effect relationship between the cell anti-radical and pro-survival effects of nanoceria. Sm doping, which decreases Ce+3 and increases oxygen vacancy contents, blunts these effects, demonstrating that Ce+3/Ce+4 redox reactions are responsible for the outstanding in vivo properties of nanoceria
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