Josefina Méndez

Gold nanoparticles (AuNPs) are one of the most remarkable nanomaterials. Due to their small size, these NPs can cross the blood–brain barrier making them good candidates for the treatment of diseases related to the central nervous system. The main objective of the present work was to evaluate the influence of surface charge on the biological behaviour of AuNPs by assessing the cytotoxic—viability and morphological alterations—and genotoxic—double strand breaks—effects induced in neuronal cells exposed to AuNPs with different charges: cationic, anionic, and neutral. Different toxicological behaviours were obtained depending on the surface charge of the NPs.

Despite being one of the most studied nanomaterials, much remains unknown about the mechanism of action of zinc oxide (ZnO) nanoparticles (NP). The aim of this work was to evaluate the effects on cell viability caused by the exposure of glial cells to ZnO NP, and the role of Zn²⁺ in the observed effects. The impact of ZnO NP or Zn²⁺ ions on cell viability was assessed by MTT assay. The exposure to ZnO NP induced a significant decrease in cell viability. The presence of Zn²⁺ ions released from ZnO NP was not entirely responsible for the observed cytotoxic effects.

Cerium dioxide nanoparticles (CeO₂NP) show antioxidant enzyme-like properties and reactive oxygen species (ROS) scavenging activity, making them a promising material for potential therapeutic applications in neurodegenerative diseases. The objective of this work was to assess the biological behavior of CeO₂NP in human SH-SY5Y neuronal and A172 glial cells by means of the MTT assay and the γH2AX assay. Despite the significant dose- and time-dependent NP internalization by both cell lines, nanoceria generally presented scarce cytotoxicity or genotoxicity, essentially restricted to the highest NP doses and longest exposure times. In conclusion, a high biocompatibility of CeO₂NP was observed under the conditions tested.

Clam farmers worldwide face several challenges, including irregular seed supply and high mortalities due to pathogenic organisms such asPerkinsus olseni. In Europe, there is a high unmet consumer demand for native clam species such asRuditapes decussatus. The high market value ofR. decussatusmakes the culture of this species potentially more attractive than that culture of the alien speciesRuditapes philippinarum. Thus, there is a market opportunity in breeding and producingR. decussatusat an industrial scale. A selective breeding program to improveR. decussatusperformance will be carried out in Portugal; and the first critical step to develop such a breeding program is the establishment of a founder population. In this study, intra- and interpopulation genetic diversity was assessed using 13 microsatellite markers in eight natural beds located in Portugal, Spain and Italy. Also, allele and genotypic frequencies of each microsatellite locus were assessed discriminating between clams infected and non-infected byP. olseni. All locations showed similar values for several genetic diversity parameters. Analyses of population differentiation (F_ST, Bayesian clustering and AMOVAs) revealed five genetically differentiated regions: Rías Altas and Rías Baixas (NW Spain), North/Central Coast of Portugal, Gulf of Cadiz and Adriatic Sea. Significant differences in the allelic and genotypic frequency distribution between infected clams and non-infected ones at four microsatellite loci are reported suggesting that resistance to the disease could have a genetic basis. Moreover, a positive or negative relationship between the frequency of certain alleles and the parasite infection was inferred. Further studies should confirm the potential use of those alleles as genetic markers forP. olseniinfection. Integrating results of genetic diversity within and between populations andPerkinsusinfection levels, a founder population for aR. decussatusbreeding program is proposed, composed by individuals from Barallobre (Rías Altas), Pontevedra or Cangas (Rías Baixas), Óbidos (North/Central Coast of Portugal), Algarve (Gulf of Cadiz) and Venice (Adriatic Sea).

The whole repeat unit of 5S rDNA and the internal transcribed spacer (ITS) of four European Donax species were analysed. After amplifying, cloning and sequencing several 5S and ITS units, their basic features and their variation were described. The phylogenetic usefulness of 5S and ITS sequences in the inference of evolutionary relationships among these wedge clams was also investigated. The length of the 5S repeat presented little variation among species, except D. trunculus that differed from the rest of the Donax species in 170–210 bp. The deduced coding region covered 120 bp, and showed recognizable internal control regions (ICRs) involved in the transcription. The length of non-transcribed spacer region (NTS) ranged from 157 bp to 165 bp in Donax trunculus and from 335 bp to 367 bp in the other three species. The conservation degree of transcriptional regulatory regions was analysed revealing a conserved TATA-like box in the upstream region. Regarding ITS sequences, the four Donax species showed slight size differences among clones due to the variation occurring in the ITS1 and ITS2, except Donax variegatus did not display size differences in the ITS2. The total length of the ITS sequence ranged between 814 and 1014 bp. Resulting phylogenetic trees display that the two ribosomal DNA regions provide well-resolved phylogenies where the four European Donax species form a single clade receiving high support in nodes. The topology obtained with 5S sequences was in agreement with Donax evolutionary relationships inferred from several sequences of different nature in previous studies. This is not only a basic research work, where new data and new knowledge is provided about Donax species, but also have allowed the authentication of these wedge clams and offers future applications to provide other genetic resources.

The harmful effects of diarrhetic shellfish poisoning (DSP) toxins on mammalian cell lines have been widely assessed. Studies in bivalves suggest that mussels display a resistance to the cytogenotoxic effects of DSP toxins. Further, it seems that the bigger the exposure, the more resistant mussels become. To elucidate the early genetic response of mussels against these toxins, the digestive gland and the gill transcriptomes of Mytilus galloprovincialis after Prorocentrum lima exposure (100,000 cells/L, 48 h) were de novo assembled based on the sequencing of 8 cDNA libraries obtained using an Illumina HiSeq 2000 platform. The assembly provided 95,702 contigs. A total of 2286 and 4523 differentially expressed transcripts were obtained in the digestive gland and the gill, respectively, indicating tissue-specific transcriptome responses. These transcripts were annotated and functionally enriched, showing 44 and 60 significant Pfam families in the digestive gland and the gill, respectively. Quantitative PCR (qPCR) was performed to validate the differential expression patterns of several genes related to lipid and carbohydrate metabolism, energy production, genome integrity and defense, suggesting their participation in the protective mechanism. This work provides knowledge of the early response against DSP toxins in the mussel M. galloprovincialis and useful information for further research on the molecular mechanisms of the bivalve resistance to these toxins.

The wedge clam, Donax trunculus (Linnaeus, 1758), is an ecologically and economically important species found in the warm waters of the Atlantic and Mediterranean areas. Donax trunculus has been suffering from a severe population decline in some wild stocks of the Iberian Peninsula, and genetic monitoring of wild populations can provide valuable information to support conservation measures and management policies. In this study, mitochondrial 16S rDNA (16S) and cytochrome b (Cytb) gene variation was examined at 18 localities across the Iberian Peninsula to test whether the patterns of genetic diversity, population structure, and demographic inferences previously deduced by using microsatellites are supported by these molecular markers. Samples (N = 557) were collected from 18 localities of the Iberian Peninsula and attention was paid to the north‐western Atlantic area, where wild stocks have diminished greatly. Analysis of molecular variance, fixation index (F_ST), and demographic inferences were estimated based on mitochondrial DNA. Since D. trunculus shows doubly uniparental inheritance, both types of mitochondrial DNA (F and M) were analysed. A high level of genetic diversity was detected using the haplotype diversity dataset, showing different geographic patterns. F_ST values for the M type revealed significant differentiation between populations on both sides of the Almeria–Oran front, and between the locality from the Alboran Sea (FU) and localities from the Atlantic Ocean. However, the F type did not detect the differentiation of FU. This makes the M genome sequences more suitable for investigating genetic structure of D. trunculus populations. Management and recovering strategies of this important resource should consider the genetic structure observed. Several strategies for conservation and management of this commercial and ecologically important bivalve are proposed.