1,721,032 research outputs found
Risposte molecolari e cellulari dei sistemi di biotrasformazione e delle difese antiossidanti in organismi marini modello
No full textI sistemi antiossidanti e della biotrasformazione sono noti per la sensibilità di risposta agli stress
ambientali, pertanto negli organismi marini vengono usati come biomarkers della contaminazione,
misurati a livello di attività catalitica e/o di espressione genica. Tuttavia, i meccanismi di
modulazione di questi sistemi e le relazioni tra risposte trascrizionali e funzionali sono ancora in
parte sconosciuti nelle specie marine. Per approfondire tali meccanismi sono state utilizzate due
specie, l’anguilla A. anguilla e il mitilo M. galloprovincialis, rappresentative di vertebrati ed
invertebrati marini. Esposizioni di laboratorio a miscele di contaminanti hanno evidenziato
differenze di risposta dipendenti da specie, tessuto e sistema enzimatico analizzato. Le risposte
catalitiche degli enzimi della biotrasformazione sono risultate comparabili alle corrispondenti
risposte trascrizionali; le risposte antiossidanti hanno mostrato una mancanza di corrispondenza tra
variazioni trascrizionali e catalitiche, suggerendo meccanismi di regolazione indipendenti a livello
biochimico e genico. Nei mammiferi, i geni antiossidanti sono regolati dal fattore di trascrizione
Nrf2 e dal suo inibitore Keap1. L’identificazione di Nrf2 e Keap1 in A. anguilla ha confermato che
tale via di regolazione è conservata nelle specie marine. I risultati ottenuti in condizioni
sperimentali di pressione ossidativa evidenziano la regolazione coordinata dei geni antiossidanti e
l’attivazione trascrizionale di Nrf2 e Keap1, suggerendo inoltre l’importanza della sintesi de novo di
Nrf2 per l’induzione prolungata dei geni target e un possibile ruolo di Keap1 nello spegnimento
della risposta.
Nel complesso, i risultati indicano che le risposte trascrizionali possono essere sensibili ma non
corrispondono necessariamente a effetti funzionali, risultando più utili come biomarkers “di
esposizione” che “di effetto”, e ampliano la conoscenza dei meccanismi di risposta antiossidante
nelle specie marine
Oxidative pathways of chemical toxicity and oxidative stress biomarkers in marine organisms.
No full textIdentification of the Nrf2-Keap1 pathway in the European eel Anguilla anguilla: role for a transcriptional regulation of antioxidant genes in aquatic organisms.
No full textAntioxidant defences play a central role in cell protection against a wide variety of environmental stressors, their variations being thus frequently studied to reveal oxidative stress conditions in fish. The Nrf2-Keap1 pathway is among the main mechanisms of transcriptional regulation in mammalians, but its involvement in modulation of antioxidant system of aquatic organisms is still largely unexplored. The present study focused on the identification of Nrf2 and Keap1 in the European eel Anguilla anguilla using liver slices as an in vitro model during an oxidative challenge. The mRNA levels of Nrf2, Keap1 and typical Nrf2 target genes (catalase, glutathione peroxidase 1 and glutathione S-transferase pi) were analysed at different H2O2 exposure times to investigate the time-course activation of these molecular responses. Obtained results showed a coordinated transcriptional regulation of CAT, GPx1 and GSTpi, also suggesting that Nrf2 de novo synthesis is required for the protracted induction of such antioxidant genes. Further, Keap1 variations would support its role in switching off these molecular responses, providing novel insight on the importance of the Nrf2-Keap1 pathway in the regulation of antioxidant genes in marine species
Oxidative metabolism of chemical pollutants in marine organisms: molecular and biochemical biomarkers in environmental toxicology.
No full textOxidative stress biomarkers are widely used in marine ecotoxicology. Environmental pollutants enhance intracellular formation of oxyradicals through several mechanisms, but complex oxidative interactions occur in response to chemical mixtures. Metabolism of individual classes of pollutants can be influenced by a sophisticated network of prooxidant relationships, reciprocal and cascade effects, changes of redox-sensitive signaling proteins, and transcription factors. Chemically mediated pathways can affect antioxidant responses at different levels, including pretranscriptional, transcriptional, protein, and catalytic functions; such mechanisms remain largely unexplored in marine organisms. Molecular responses of antioxidants are frequently not paralleled by expected biochemical changes or cellular effects, and caution is needed when interpreting the effects of environmental pollutants. Results on antioxidant variations can be influenced by mRNA stability and protein turnover, different timing for transcriptional and translational mechanisms, metabolic capability of tissues, posttranscriptional modifications of proteins, biphasic responses of antioxidant enzymes, and adaptation mechanisms to chronic pollution
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
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