ADULT SOD1 G93R ZEBRAFISH MODEL DEVELOPS HALLMARK FEATURES OF ALS AND DISPLAYS NEUROMUSCULAR JUNCTIONS DEFECTS AND SPINAL NEURONS HYPEREXCITABILITY AT EARLY DEVELOPMENTAL STAGES

Amyotrophic Lateral Sclerosis (ALS) is an adult-onset neurodegenerative disease characterized by selective and progressive loss of motor neurons in the spinal cord, brain stem and motor cortex. Approximately 12% of familial and 1% of sporadic cases of ALS are associated to mutations in the gene coding for the antioxidant enzyme Cu-Zn Superoxide Dismutase type 1 (SOD1). Zebrafish is emerging as a powerful experimental model for the study of disorders affecting the nervous system and here we characterized the disease phenotype in adult zebrafish overexpressing the Sod1 ALS-linked mutation G93R (mSod1) and the wild-type Sod1 (wtSod1). Adult zebrafish expressing mutant Sod1 develop most of the main pathological features occurring in ALS: locomotor impairments, motor neurons degeneration, spinal cord and muscle atrophy, neuromuscular junctions loss, astrogliosis and inflammation. Interestingly, as it was reported in mice models of the disease, also in this model the overexpression of the wild-type form of Sod1 is associated to the development of mild alterations. Having completed the characterization of the pathological phenotype in the adult, we searched for precocious ALS hallmarks in zebrafish embryos and larvae. The optical transparency of zebrafish at early developmental stages allowed us to perform whole-mount fluorescence staining from which we studied the effects of the overexpression of wild-type or mutant Sod1 on spinal motor neurons development and neuromuscular junctions maturation. Mutant zebrafish embryos display precocious motor nerves branching defects while larvae present neuromuscular junctions maturation impairments and muscle fibers atrophy. The expression of mutant Sod1 is associated to precocious behavioral alterations in spontaneous tail coilings at 20 hpf, in touched evoked tail coiling responses at 48 hpf and in burst swimming responses at 96 hpf. In Sod1 G93R expressing embryos we detected spinal neurons hyperexcitability associated to the increased activity of the persistent sodium current INaP, and by the administration of riluzole, directly into the embryo water, we managed to pharmacologically modulate the spinal neurons electrical activity, the behavioral phenotype and the motor axons length. These results are extremely relevant since several studies demonstrated that ALS patients exhibit cortical hyperexcitability before any clinical sign of ALS and electrophysiological experiments performed in cultured mice embryonic and neonatal dissociated spinal motor neurons expressing mutant SOD1 G93A demonstrated neuronal hyperexcitability associated to the increased activity of the persistent sodium current INaP. This work demonstrates that the Sod1 G93R zebrafish model not only represents a valuable complement to other animal model for the study of ALS but also that it is a powerful model on its own to investigate ALS mainly thanks to the possibility to study locomotor circuits and potential pathogenetic mechanisms occurring at the very early stages of disease pathogenesis

Fundamental Understanding of Poly(ether ketone ketone) for High Temperature Laser Sintering

High-Temperature Laser Sintering (HT-LS) is a powder bed fusion technique employed to manufacture polymers with high service temperature, usually above 150 oC. The aerospace, automotive, and medical industries have driven the demand for processing high-performance polymers, as they could offer a lighter and cheaper alternative while maintaining the mechanical and chemical performance required to replace metallic parts in particular environments. Kepstan 6002 poly(ether ketone ketone) (PEKK) belongs to poly(aryl ether ketone)s (PAEKs) family and has a promising application in LS. The lower melting temperature united to the high glass transition temperature of PEKK (similar to PEK HP3, first commercially available HT-LS grade) enabled processing at lower temperatures whilst maintaining the high-temperature resistance of the polymer. Furthermore, the kinetics of crystallisation of Kepstan 6002 PEKK is very slow, which can assist layer adhesion during LS and improve mechanical properties in Z orientation. The present research project was developed in collaboration with Arkema. Three different grades of Kepstan 6002 PEKK were selected for initial analyses – HL1327, HL1320, and P12S959a. The powders were characterised for powder size, distribution, morphology, flow, moisture effect, and coalescence behaviour. This screening enabled the selection of HL1327 grade as the most promising for HT-LS application. The PEKK particle and powder analyses continued with an in-depth study of particle size and shape changes as a function of temperature and coalescence. The study revealed individual particle shrinkage prior to melting, followed by increased growth. The same phenomenon was observed for pairs of particles during coalescence and was attributed to the recovering of elastic deformation of the polymeric chains. The effect of intrinsic PEKK characteristics was successfully evaluated and quantified in the overall shrinkage in LS. The results identified powder properties as the main factor causing shrinkage of PEKK, as opposed to crystallisation. These results are supported by the powder characterisation developed in previous chapters. The interaction between material and process was investigated and optimised by testing different combinations of laser parameters and processing temperatures. The resulting properties were monitored regarding mechanical performance, surface topography, porosity, and crystallisation. The optimised PEKK specimens showed excellent mechanical strength (∼90 MPa) and modulus, but poor elongation, a common drawback from the LS process. The combination of fundamental material properties and process optimisation led to the development of a novel route to improve elongation and control the mechanical performance of LS PEKK. The experimental method successfully related cooling time, mechanical properties, and crystallisation of PEKK, and was able to increase elongation at break by 5.4 times. The improvement of elongation at break was attributed to the largely amorphous phase of PEKK when subjected to short cooling times. Lastly, powder recyclability was investigated from a chemical and physical perspective. PEKK can be reused following additional treatment steps, e.g., sieving. The potential for recyclability is an important remark as the material cost is significantly reduced and therefore preferred over the use of metals for high-performance applications

Real-time monitoring of proton exchange membrane fuel cell stack failure

Uneven pressure drops in a 75-cell 9.5-kWe proton exchange membrane fuel cell stack with a U-shaped flow configuration have been shown to cause localised flooding. Condensed water then leads to localised cell heating, resulting in reduced membrane durability. Upon purging of the anode manifold, the resulting mechanical strain on the membrane can lead to the formation of a pin-hole/membrane crack and a rapid decrease in open circuit voltage due to gas crossover. This failure has the potential to cascade to neighbouring cells due to the bipolar plate coupling and the current density heterogeneities arising from the pin-hole/membrane crack. Reintroduction of hydrogen after failure results in cell voltage loss propagating from the pin-hole/membrane crack location due to reactant crossover from the anode to the cathode, given that the anode pressure is higher than the cathode pressure. Through these observations, it is recommended that purging is avoided when the onset of flooding is observed to prevent irreparable damage to the stack

Echinococcosis of the Liver: Report of a Case

Echinococcosis of the liver is so rare in our practice that the case presented is the only one documented in the records of Henry Ford Hospital. The massive enlargement of the liver required surgical intervention. Marsupialization was the treatment of choice. In spite of post-operative complications, the patient made a satisfactory recovery

Trophic compensation stabilizes marine primary producers exposed to artificial light at night

Artificial light at night (ALAN) is a widespread phenomenon along coastal areas. Despite in - creasing evidence of pervasive effects of ALAN on patterns of species distribution and abundance, the potential of this emerging threat to alter ecological processes in marine ecosystems has remained largely unexplored. Here, we show how exposure to white LED lighting, comparable to that experienced along local urbanized coasts, significantly enhanced the impact of grazing gastropods on epilithic microphytobenthos (MPB). ALAN increased both the photo-synthetic biomass of MPB and the grazing pressure of gastropods, such that consumers compensated for the positive effect of night lighting on primary producers. Our results indicate that trophic interactions can provide a stabilizing compensatory mechanism against ALAN effects in natural food webs

Fractal Structure of Loop Quantum Gravity

In this paper we have calculated the spectral dimension of loop quantum gravity (LQG) using simple arguments coming from the area spectrum at different length scales. We have obtained that the spectral dimension of the spatial section runs from 2 to 3, across a 1.5 phase, when the energy of a probe scalar field decrees from high to low energy. We have calculated the spectral dimension of the space-time also using results from spin-foam models, obtaining a 2-dimensional effective manifold at hight energy. Our result is consistent with other two approach to non perturbative quantum gravity: causal dynamical triangulation and asymptotic safety quantum gravity.Comment: 5 pages, 5 figure

Spatial structures and dynamics of kinetically constrained models for glasses

Kob and Andersen's simple lattice models for the dynamics of structural glasses are analyzed. Although the particles have only hard core interactions, the imposed constraint that they cannot move if surrounded by too many others causes slow dynamics. On Bethe lattices a dynamical transition to a partially frozen phase occurs. In finite dimensions there exist rare mobile elements that destroy the transition. At low vacancy density, $v$, the spacing, $\Xi$, between mobile elements diverges exponentially or faster in $1/v$. Within the mobile elements, the dynamics is intrinsically cooperative and the characteristic time scale diverges faster than any power of $1/v$ (although slower than $\Xi$). The tagged-particle diffusion coefficient vanishes roughly as $\Xi^{-d}$.Comment: 4 pages. Accepted for pub. in Phys. Rev. Let