Mitigating human disturbance: can protection influence trajectories of recovery in benthic assemblages?

1. Understanding whether Marine Protected Areas (MPAs) can be considered as a suitable tool for restoring the structure and function of populations and assemblages is urgently needed to achieve an effective policy of mitigation of human impact in coastal management. However, to date, the role played by MPAs in enhancing ecosystems resilience has been more advocated than unambiguously documented. 2. This study was designed to test whether full protection in marine reserves facilitates recovery of benthos impacted by the date mussel Lithophaga lithophaga fishery, one of the most harmful human activities affecting subtidal rocky habitats in the Mediterranean Sea. 3. The effects of this destructive fishery were reproduced at one fully protected location (P) and at two unprotected control locations (Cs) in the SW Mediterranean Sea. At each location, three plots (4 m2) of rocky surface at 4-6 m depth were disturbed experimentally, while another three plots served as reference. In each plot, the species composition and relative cover of the sessile benthic assemblages were sampled photographically on each of five occasions during a period of 20 months. 4. Over and above variation in habitat features among locations, multivariate and univariate analyses revealed significant differences between P-vs.-Cs in patterns of assemblage recovery and showed that, at the fully protected location, recovery was faster than at the unprotected control locations. 5. Our results suggest that MPAs have the potential to change the trajectories of recovery of disturbed assemblages by accelerating the processes of recolonization and call for further investigation to identify the specific mechanisms underlying increased resilience.     

Magnetic resonance imaging of tumor cells by targeting the amino acid transport system

An early diagnosis of cancer is crucial in the battle against this disease and the in vivo visualization of tumors at cellular level is still the most challenging goal. In order to target tumor cells, we took into account their increased metabolism and amino acid nutrients or pseudo-nutrients, which are actively transported through the cell membrane, have been chosen as vectors for new MRI contrast agents. For this reason new gadolinium complexes conjugated to agmatine, arginine, and glutamine have been synthesized and studied.     

The origin and evolution of Archaea: a state of the art

Environmental surveys indicate that the Archaea are diverse and abundant not only in extreme environments, but also in soil, oceans and freshwater, where they may fulfil a key role in the biogeochemical cycles of the planet. Archaea display unique capacities, such as methanogenesis and survival at temperatures higher than 90 degrees C, that make them crucial for understanding the nature of the biota of early Earth. Molecular, genomics and phylogenetics data strengthen Woese's definition of Archaea as a third domain of life in addition to Bacteria and Eukarya. Phylogenomics analyses of the components of different molecular systems are highlighting a core of mainly vertically inherited genes in Archaea. This allows recovering a globally well-resolved picture of archaeal evolution, as opposed to what is observed for Bacteria and Eukarya. This may be due to the fact that no rapid divergence occurred at the emergence of present-day archaeal lineages. This phylogeny supports a hyperthermophilic and non-methanogenic ancestor to present-day archaeal lineages, and a profound divergence between two major phyla, the Crenarchaeota and the Euryarchaeota, that may not have an equivalent in the other two domains of life. Nanoarchaea may not represent a third and ancestral archaeal phylum, but a fast-evolving euryarchaeal lineage. Methanogenesis seems to have appeared only once and early in the evolution of Euryarchaeota. Filling up this picture of archaeal evolution by adding presently uncultivated species, and placing it back in geological time remain two essential goals for the future.     

Microenvironmental pH Is a Key Factor for Exosome Traffic in Tumor Cells

Exosomes secreted by normal and cancer cells carry and deliver a variety of molecules. To date, mechanisms referring to tumor exosome trafficking, including release and cell-cell transmission, have not been described. To gain insight into this, exosomes purified from metastatic melanoma cell medium were labeled with a lipid fluorescent probe, R18, and analyzed by spectrofluorometry and confocal microscopy. A low pH condition is a hallmark of tumor malignancy, potentially influencing exosome release and uptake by cancer cells. Using different pH conditions as a modifier of exosome traffic, we showed (i) an increased exosome release and uptake at low pH when compared with a buffered condition and (ii) exosome uptake by melanoma cells occurred by fusion. Membrane biophysical analysis, such as fluidity and lipid composition, indicated a high rigidity and sphingomyelin/ganglioside GM3 (N-acetylneuraminylgalactosylglucosylceramide) content in exosomes released at low pH. This was likely responsible for the increased fusion efficiency. Consistent with these results, pretreatment with proton pump inhibitors led to an inhibition of exosome uptake by melanoma cells. Fusion efficiency of tumor exosomes resulted in being higher in cells of metastatic origin than in those derived from primary tumors or normal cells. Furthermore, we found that caveolin-1, a protein involved in melanoma progression, is highly delivered through exosomes released in an acidic condition. The results of our study provide the evidence that exosomes may be used as a delivery system for paracrine diffusion of tumor malignancy, in turn supporting the importance of both exosomes and tumor pH as key targets for future anti-cancer strategies.     

<Emphasis Type="Italic">Anisakis nascettii</Emphasis> n. sp. (Nematoda: Anisakidae) from beaked whales of the southern hemisphere: morphological description,genetic relationships between congeners and ecological data

A new anisakid nematode, Anisakis nascettii n. sp., is described from beaked whales Mesoplodon spp. off the coast of New Zealand and South Africa. Morphological and molecular (allozymes and mtDNA cox2 sequence) data were used for diagnostic and identification purposes. Among the 19 allozymes studied, 10 were found to be unique and characteristic for A. nascettii n. sp. Analysis of allozymes demonstrated reproductive isolation from A. ziphidarum Paggi, Nascetti, Webb, Mattiucci, Cianchi & Bullini, 1998 and mtDNA cox2 sequences depict this Anisakis species as a distinct and unique entity. Key morphological diagnostic traits for A. nascettii with respect to the genetically closely related species A. ziphidarum include: spicule length, the spicule/body length ratio, the arrangement of the caudal papillae and the shape of the plectanes of the adult males. Genetic data confirmed that Anisakis sp. A of Pontes et al. (2005), which was partly described by Iglesias et al. (2008), and Anisakis sp. of Valentini et al. (2006) are conspecific with A. nascettii. Both molecular and morphological data indicate that the new species belongs to the ‘ziphidarum-group’; however, it is genetically very distinct from A. ziphidarum (D _Nei  = 0.69, K2P = 0.09), as well as from all of the previously genetically characterised Anisakis spp. All tree topologies inferred by different methods (MP, NJ and Bayesian) support the finding that A. nascettii n. sp. and A. ziphidarum are sister-species. It is also confirmed that A. nascettii n. sp. is, at the adult stage, a parasite of beaked whales of the genus Mesoplodon, whereas, as a larva, it has been identified from the squid Moroteuthis ingens Smith. Furthermore, Mesoplodon bowdoini Andrews represents a new host record for A. ziphidarum. The parallelism between the clade formed by these two anisakine taxa, i.e. A. ziphidarum and A. nascettii, and that formed by their definitive hosts further supports the hypothesis of host–parasite co-evolutionary relationships, as previously suggested for Anisakis spp. and their cetacean hosts.     

Cdc14 Inhibition by the Spindle Assembly Checkpoint Prevents Unscheduled Centrosome Separation in Budding Yeast

The spindle assembly checkpoint (SAC) is an evolutionarily conserved surveillance mechanism that delays anaphase onset and mitotic exit in response to the lack of kinetochore attachment. The target of the SAC is the E3 ubiquitin ligase anaphase-promoting complex (APC) bound to its Cdc20 activator. The Cdc20/APC complex is in turn required for sister chromatid separation and mitotic exit through ubiquitin-mediated proteolysis of securin, thus relieving inhibition of separase that unties sister chromatids. Separase is also involved in the Cdc-fourteen early anaphase release (FEAR) pathway of nucleolar release and activation of the Cdc14 phosphatase, which regulates several microtubule-linked processes at the metaphase/anaphase transition and also drives mitotic exit. Here, we report that the SAC prevents separation of microtubule-organizing centers (spindle pole bodies [SPBs]) when spindle assembly is defective. Under these circumstances, failure of SAC activation causes unscheduled SPB separation, which requires Cdc20/APC, the FEAR pathway, cytoplasmic dynein, and the actin cytoskeleton. We propose that, besides inhibiting sister chromatid separation, the SAC preserves the accurate transmission of chromosomes also by preventing SPBs to migrate far apart until the conditions to assemble a bipolar spindle are satisfied.     

The Influence of Catalysis on Mad2 Activation Dynamics

Mad2 is a key component of the spindle assembly checkpoint, a safety device ensuring faithful sister chromatid separation in mitosis. The target of Mad2 is Cdc20, an activator of the anaphase-promoting complex/cyclosome (APC/C). Mad2 binding to Cdc20 is a complex reaction that entails the conformational conversion of Mad2 from an open (O-Mad2) to a closed (C-Mad2) conformer. Previously, it has been hypothesized that the conversion of O-Mad2 is accelerated by its conformational dimerization with C-Mad2. This hypothesis, known as the Mad2-template hypothesis, is based on the unproven assumption that the natural conversion of O-Mad2 required to bind Cdc20 is slow. Here, we provide evidence for this fundamental assumption and demonstrate that conformational dimerization of Mad2 accelerates the rate of Mad2 binding to Cdc20. On the basis of our measurements, we developed a set of rate equations that deliver excellent predictions of experimental binding curves under a variety of different conditions. Our results strongly suggest that the interaction of Mad2 with Cdc20 is rate limiting for activation of the spindle checkpoint. Conformational dimerization of Mad2 is essential to accelerate Cdc20 binding, but it does not modify the equilibrium of the Mad2:Cdc20 interaction, i.e., it is purely catalytic. These results surpass previously formulated objections to the Mad2-template model and predict that the release of Mad2 from Cdc20 is an energy-driven process.