Browsing by Author "Vasconcelos, Vítor"
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- Absence of negative allelopathic effects of cylindrospermopsin and microcystin-LR on selected marine and freshwater phytoplankton speciesPublication . Pinheiro, Carlos; Azevedo, Joana; Campos, Alexandre; Loureiro, Susana; Vasconcelos, VítorCyanobacterial toxins have been regarded by some researchers as allelopathic substances that could modulate the growth of competitors. Nevertheless, often the concentrations of toxins used are too high to be considered ecologically relevant. In this work we tested the hypothesis that microcystin-LR (MC-LR) and cylindrospermopsin (CYN) at ecologically relevant concentrations have no allelopathic effects on some species of phytoplankton. Extracts containing the toxins as well as pure MC-LR and CYN toxins were used to assess their effects on the growth rates of Nannochloropsis sp., Chlamydomonas reinhardtii, and Chlorella vulgaris. Cyanobacterial crude extracts induced more pronounced effects on growth rates than pure toxins. Microcystis aeruginosa and Aphanizomenon ovalisporum crude extracts containing MC-LR and CYN at 0.025–2.5 mg l−1 stimulated growth rates of microalgae, whereas A. ovalisporum crude extracts containing 2.5 mg l−1 of CYN strongly inhibited growth rates of microalgae after 4 and 7 days of exposure. MC-LR and CYN at environmentally occurring concentrations were unable to affect negatively the growth of microalgae, and therefore these molecules may play roles other than allelopathy in natural ecosystems.
- Antimicrobial and cytotoxic assessment of marine cyanobacteria - synechocystis and synechococcusPublication . Martins, Rosario; Ramos, Miguel; Herfindal, Lars; Sousa, José; Skærven, Kaja; Vasconcelos, VítorAqueous extracts and organic solvent extracts of isolated marine cyanobacteria strains were tested for antimicrobial activity against a fungus, Gram-positive and Gram-negative bacteria and for cytotoxic activity against primary rat hepatocytes and HL-60 cells. Antimicrobial activity was based on the agar diffusion assay. Cytotoxic activity was measured by apoptotic cell death scored by cell surface evaluation and nuclear morphology. A high percentage of apoptotic cells were observed for HL-60 cells when treated with cyanobacterial organic extracts. Slight apoptotic effects were observed in primary rat hepatocytes when exposed to aqueous cyanobacterial extracts. Nine cyanobacteria strains were found to have antibiotic activity against two Gram-positive bacteria, Clavibacter michiganensis subsp. insidiosum and Cellulomonas uda. No inhibitory effects were found against the fungus Candida albicans and Gram-negative bacteria. Marine Synechocystis and Synechococcus extracts induce apoptosis in eukaryotic cells and cause inhibition of Gram-positive bacteria. The different activity in different extracts suggests different compounds with different polarities.
- Antioxidant and oxidative stress responses in zebrafish brain after exposure to low doses of ionizing radiationPublication . Lemos, Joana; Guimarães, Laura; Vasconcelos, Vítor; Ponte, Fernanda; Costa, Paulo; Metello, Luís F.; Carvalho, António PauloIntroduction: The use of zebrafish – Danio rerio – has grown considerably, demonstrating the increasing interest to use this model in biomedical research. This is essentially due to the level of homology shared with the human genome, complemented by an easy and reasonably affordable practical side. Hence, this work investigated radiobiological effects of exposure to low doses of ionizing radiation in zebrafish.
- Antitumor activity of hierridin B, a cyanobacterial secondary metabolite found in both filamentous and unicellular marine strainsPublication . Leão, Pedro N.; Costa, Margarida; Ramos, Vitor; Pereira, Alban R.; Fernandes, Virgínia C.; Domingues, Valentina F.; Gerwick, William H.; Vasconcelos, Vítor; Martins, RosárioCyanobacteria are widely recognized as a valuable source of bioactive metabolites. The majority of such compounds have been isolated from so-called complex cyanobacteria, such as filamentous or colonial forms, which usually display a larger number of biosynthetic gene clusters in their genomes, when compared to free-living unicellular forms. Nevertheless, picocyanobacteria are also known to have potential to produce bioactive natural products. Here, we report the isolation of hierridin B from the marine picocyanobacterium Cyanobium sp. LEGE 06113. This compound had previously been isolated from the filamentous epiphytic cyanobacterium Phormidium ectocarpi SAG 60.90, and had been shown to possess antiplasmodial activity. A phylogenetic analysis of the 16S rRNA gene from both strains confirmed that these cyanobacteria derive from different evolutionary lineages. We further investigated the biological activity of hierridin B, and tested its cytotoxicity towards a panel of human cancer cell lines; it showed selective cytotoxicity towards HT-29 colon adenocarcinoma cells.
- Application of real-time PCR in the assessment of the toxic cyanobacterium cylindrospermopsis raciborskii abundance and toxicological potentialPublication . Moreira, Cristiana; Martins, António; Azevedo, Joana; Freitas, Marisa; Regueiras, Ana; Vale, Micaela; Antunes, Agostinho; Vasconcelos, VítorCyanobacteria are prokaryotic photosynthetic microorganisms that pose a serious threat to aquatic environments because they are able to form blooms under eutrophic conditions and produce toxins. Cylindrospermopsis raciborskii is a planktonic heterocystous filamentous cyanobacterium initially assigned to the tropics but currently being found in more temperate regions such as Portugal, the southernmost record for this species in Europe. Cylindrospermopsin originally isolated from C. raciborskii is a cytotoxic alkaloid that affects the liver, kidney, and other organs. It has a great environmental impact associated with cattle mortality and human morbidity. Aiming in monitoring this cyanobacterium and its related toxin, a shallow pond located in the littoral center of Portugal, Vela Lake, used for agriculture and recreational purposes was monitored for a 2-year period. To accomplish this, we used the real-time PCR methodology in field samples to quantify the variation of specific genetic markers with primers previously described characterizing total cyanobacteria (16S rRNA), C. raciborskii (rpoC1), and cylindrospermopsin synthetase gene (pks). The results report the high abundance of both cyanobacteria and C. raciborskii in Vela Lake, with C. raciborskii representing 0.4% to 58% of the total cyanobacteria population. Cylindrospermopsin synthetase gene was detected in one of the samples. We believe that with the approach developed in this study, it will be possible to monitor C. raciborskii population dynamics and seasonal variation, as well as the potential toxin production in other aquatic environments.
- Are known cyanotoxins involved in the toxicity of picoplanktonic and filamentous north atlantic marine cyanobacteria?Publication . Frazão, Bárbara; Martins, Rosario; Vasconcelos, VítorEight marine cyanobacteria strains of the genera Cyanobium, Leptolyngbya, Oscillatoria, Phormidium, and Synechococcus were isolated from rocky beaches along the Atlantic Portuguese central coast and tested for ecotoxicity. Strains were identified by morphological characteristics and by the amplification and sequentiation of the 16S rDNA. Bioactivity of dichloromethane, methanol and aqueous extracts was assessed by the Artemia salina bioassay. Peptide toxin production was screened by matrix assisted laser desorption/ionization time of flight mass spectrometry. Molecular analysis of the genes involved in the production of known cyanotoxins such as microcystins, nodularins and cylindrospermopsin was also performed. Strains were toxic to the brine shrimp A. salina nauplii with aqueous extracts being more toxic than the organic ones. Although mass spectrometry analysis did not reveal the production of microcystins or other known toxic peptides, a positive result for the presence of mcyE gene was found in one Leptolyngbya strain and one Oscillatoria strain. The extensive brine shrimp mortality points to the involvement of other unknown toxins, and the presence of a fragment of genes involved in the cyanotoxin production highlight the potential risk of cyanobacteria occurrence on the Atlantic coast.
- Assessing Radiobiological Effects of Low Doses of Ionizing Radiation on Zebrafish by Bidimensional Gel ElectrophoresisPublication . Lemos, Joana; Costa, Pedro; Cunha, Lídia; Campos, Alexandre; Carvalho, António Paulo; Vasconcelos, Vítor; Genésio, Paula; Ponte, Fernanda; Costa, Paulo; Crespo, Paulo; Metello, Luís F.Aim: This paper relates with a specific task from a larger research project oriented to the development and application of the Zebrafish – Danio rerio – to the study of radiobiological effects of medical diagnostic level – low doses – of ionizing radiation.
- Assessment of Constructed Wetlands’ Potential for the Removal of Cyanobacteria and Microcystins (MC-LR)Publication . Bavithra, Guna; Azevedo, Joana; Oliveira, Flávio; Morais, João; Pinto, Edgar; Ferreira, Isabel M. P. L.V. O.; Vasconcelos, Vítor; Campos, Alexandre; Almeida, C. Marisa R.Microcystis blooms and the subsequent release of hepatotoxic microcystins (MCs) pose a serious threat to the safety of water for human and livestock consumption, agriculture irrigation, and aquaculture worldwide. Microcystin-LR (MC-LR), the most toxic variant of MCs, has been widely detected in a variety of environments such as water, sediments, plants, and many aquatic organisms.
- Bioaccessibility and changes on cylindrospermopsin concentration in edible mussels over storage and processing time.Publication . Freitas, Marisa; Azevedo, Joana; Carvalho, António Paulo; Mendes, Vera; Manadas, Bruno; Campos, Alexandre; Vasconcelos, VítorThe cyanotoxin cylindrospermopsin has been recognized of increased concern due to the global expansion of its main producer, Cylindrospermopsis raciborskii. Previous studies have shown that aquatic organisms, especially bivalves, can accumulate high levels of cylindrospermopsin. Based on the potential for human health risks, a provisional tolerable daily intake of 0.03 µg/kg body-weight has been recommended. However, human exposure assessment has been based on the cylindrospermopsin concentration in raw food items. This study aimed to assess the changes on cylindrospermopsin concentration in edible mussels over storage and processing time as well as cylindrospermopsin bioaccessibility. Mussels, (Mytilus galloprovincialis) fed cylindrospermopsin-producing C. raciborskii, were subjected to the treatments and then analyzed by LC-MS/MS. Mussels stored frozen allowed a significantly higher recovery of cylindrospermopsin (52.5%/48 h and 57.7%/one week). The cooking treatments did not produce significant differences in cylindrospermopsin concentration in mussel matrices (flesh), however, cylindrospermopsin was found in the cooking water, suggesting that heat processing can be used to reduce the availability of cylindrospermopsin in this food item. The in vitro digestion with salivary and gastrointestinal juices considerably decreased the cylindrospermopsin availability in uncooked and steamed mussels, highlighting the importance in integrating the bioaccessibility in the human health risk assessment.
- Bioactivity screening of marine cyanobacteria for the isolation of novel compounds for hepatic steatosisPublication . Moreira, Gabriela A.; Rosa, Filipa; Vasconcelos, Vítor; Urbatzka, RalphNonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease and effective therapeutics has been widely study. Cyanobacteria, previously known as blue-green algae, are known to produce many secondary metabolites including toxins, with applications to the pharmaceutical industry. The aim of this study is to investigate the effect of extract from cyanobacteria to reduce lipid accumulation in a model of hepatic steatosis using HepG2 cells in vitro.