Mesophotic Coral Ecosystems in the Eastern Tropical Pacific: The current state of knowledge and the spatial variability of their depth boundaries.

In the Eastern Tropical Pacific (ETP), Mesophotic Coral Ecosystems (MCEs) are limited by oceanographic conditions and are thought to be mostly absent. However, considering the currently discussed more flexible approach to define mesophotic boundaries, based on light availability, we performed a systematic search to assess their current state of knowledge. Using MODIS-Aqua satellite data (Kd490), we calculated the mesophotic boundaries in the ETP, based on optical depths, and performed a bibliographic search of studies carried out at those depths, including those present in turbid waters with KdPAR values up to 0.2 m-1. Seventy-seven papers on MCEs research were compiled in this review, recording a total of 138 species. The studies focus almost exclusively on taxonomy, ecosystem function, and reviews, indicating the need for future research regarding aspects, such as structuring environmental variables, molecular ecology, and natural resource management. Furthermore, remote sensing data show that there exists a high spatial variability of water transparency in the ETP, resulting in significant differences in KdPAR between oceanic and continental locations, mostly related to the occurrence of seasonal upwelling in the latter. Based on KdPAR, we estimated the mesophotic depth boundaries (z10%, z1%, z0.1%) for specific locations within the ETP and found that MCEs can potentially occur as shallow as 13-15 m in coastal regions. Also, we compared the calculated boundaries with the respective deepest records of light-dependent corals. With one exception, the presence of the corals was restricted to the upper mesophotic subzone (z10%-z1%), which agrees with reports for other regions, showing that light availability is one of the main drivers for the bathymetric distribution of MCEs and can be used as a first approach to identify their potential presence, though other local factors (e.g., geomorphology, temperature, internal waves) should also be considered, as they can cause shifts in depth limits.

A Novel, Reliable and Highly Versatile Method to Evaluate Different Prion Decontamination Procedures.

Transmissible spongiform encephalopathies (TSEs) are a group of invariably fatal neurodegenerative disorders. The causal agent is an aberrantly folded isoform (PrPSc or prion) of the endogenous prion protein (PrPC) which is neurotoxic and amyloidogenic and induces misfolding of its physiological counterpart. The intrinsic physical characteristics of these infectious proteinaceous pathogens makes them highly resistant to the vast majority of physicochemical decontamination procedures used typically for standard disinfection. This means prions are highly persistent in contaminated tissues, the environment (surfaces) and, of great concern, on medical and surgical instruments. Traditionally, decontamination procedures for prions are tested on natural isolates coming from the brain of infected individuals with an associated high heterogeneity resulting in highly variable results. Using our novel ability to produce highly infectious recombinant prions in vitro we adapted the system to enable recovery of infectious prions from contaminated materials. This method is easy to perform and, importantly, results in highly reproducible propagation in vitro. It exploits the adherence of infectious prion protein to beads of different materials allowing accurate and repeatable assessment of the efficacy of disinfectants of differing physicochemical natures to eliminate infectious prions. This method is technically easy, requires only a small shaker and a standard biochemical technique and could be performed in any laboratory.

HERC1 Ubiquitin Ligase Is Required for Normal Axonal Myelination in the Peripheral Nervous System.

A missense mutation in HERC1 provokes loss of cerebellar Purkinje cells, tremor, and unstable gait in tambaleante (tbl) mice. Recently, we have shown that before cerebellar degeneration takes place, the tbl mouse suffers from a reduction in the number of vesicles available for release at the neuromuscular junction (NMJ). The aim of the present work was to study to which extent the alteration in HERC1 may affect other cells in the nervous system and how this may influence the motor dysfunction observed in these mice. The functional analysis showed a consistent delay in the propagation of the action potential in mutant mice in comparison with control littermates. Morphological analyses of glial cells in motor axons revealed signs of compact myelin damage as tomacula and local hypermyelination foci. Moreover, we observed an alteration in non-myelinated terminal Schwann cells at the level of the NMJ. Additionally, we found a significant increment of phosphorylated Akt-2 in the sciatic nerve. Based on these findings, we propose a molecular model that could explain how mutated HERC1 in tbl mice affects the myelination process in the peripheral nervous system. Finally, since the myelin abnormalities found in tbl mice are histological hallmarks of neuropathic periphery diseases, tbl mutant mice could be considered as a new mouse model for this type of diseases.

Recombinant PrP and Its Contribution to Research on Transmissible Spongiform Encephalopathies.

The misfolding of the cellular prion protein (PrPC) into the disease-associated isoform (PrPSc) and its accumulation as amyloid fibrils in the central nervous system is one of the central events in transmissible spongiform encephalopathies (TSEs). Due to the proteinaceous nature of the causal agent the molecular mechanisms of misfolding, interspecies transmission, neurotoxicity and strain phenomenon remain mostly ill-defined or unknown. Significant advances were made using in vivo and in cellula models, but the limitations of these, primarily due to their inherent complexity and the small amounts of PrPSc that can be obtained, gave rise to the necessity of new model systems. The production of recombinant PrP using E. coli and subsequent induction of misfolding to the aberrant isoform using different techniques paved the way for the development of cell-free systems that complement the previous models. The generation of the first infectious recombinant prion proteins with identical properties of brain-derived PrPSc increased the value of cell-free systems for research on TSEs. The versatility and ease of implementation of these models have made them invaluable for the study of the molecular mechanisms of prion formation and propagation, and have enabled improvements in diagnosis, high-throughput screening of putative anti-prion compounds and the design of novel therapeutic strategies. Here, we provide an overview of the resultant advances in the prion field due to the development of recombinant PrP and its use in cell-free systems.

Absorptance determinations on multicellular tissues.

The analysis of the variation of the capacity and efficiency of photosynthetic tissues to collect solar energy is fundamental to understand the differences among species in their ability to transform this energy into organic molecules. This analysis may also help to understand natural changes in species distribution and/or abundance, and differences in species ability to colonize contrasting light environments or respond to environmental changes. Unfortunately, the challenge that optical determinations on highly dispersive samples represent has strongly limited the progression of this analysis on multicellular tissues, limiting our knowledge of the role that optical properties of photosynthetic tissues may play in the optimization of photosynthesis and growth of benthonic primary producers. The aim of this study is to stimulate the use of optical tools in marine eco-physiology, offering a succinct description of the more convenient tools and also solutions to resolve the more common technical difficulties that arise while performing optical determinations on highly dispersive samples. Our study focuses on two-dimensional (2D-) parameters: absorptance, transmittance, and reflectance, and illustrates with correct and incorrect examples, specific problems and their respective solutions. We also offer a general view of the broad variation in light absorption shown by photosynthetic structures of marine primary producers, and its low association with pigment content. The ecological and evolutionary functional implications of this variability deserve to be investigated across different taxa, populations, and marine environments.