Selenoproteins in mammalian spermatogenesis:role of the nuclear GPx4

The selenoprotein Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPx/GPx4) is an enzyme unique among the various GPxs, because it is able to use protein thiols, beside glutathione, The GPx4 gene encodes for three isoforms having different subcellular localization, being located in the mitochondria (mGPx4), in the cytosol (cGPx4) and in the nucleus (nGPx4), each having distinct functions. The mGPx4 is important to male fertility, as proven by the structural abnormalities of sperm tails from KO mice specifically lacking this isoform, which make these mutants infertile. As for the nuclear isoform, nGPx4-KO mice are fertile but show impaired nuclear condensation of sperm isolated from the caput epididymis, suggesting a role in chromatin stability. To gain more insight into the functions of nGPx4, we first investigated the subnuclear localization of this form in both COS-1 cells overexpressing nGPx4 and mouse male germ cells at different steps of maturation (round spermatids and epididymal spermatozoa). We performed both biochemical and morphological analyses and found that nGPx4 was localized at the level of the nuclear matrix. To test the functional role in chromatin dynamics sperm isolated from the caput and the cauda epididymides from WT and nGPx4-KO mice were subjected to an in vitro chromatin decondensation assay. Our results show that nGPx4-KO mice sperm decondensed earlier than those from WT at all stages of epididymal maturation, providing conclusive evidence that nGPx4 is required for a correct sperm chromatin remodelling. We next addressed the issue whether the sperm nuclear structure instability caused by the lack of nGPx4 might impact on the early events occurring after fertilization. In "in vitro" fertilization experiments, we revealed that, compared to WT, nGPx4-KO mice showed an acceleration of sperm nuclear decondensation, confirming the results previously obtained

The matrix Kadomtsev--Petviashvili equation as a source of integrable nonlinear equations

A new integrable class of Davey--Stewartson type systems of nonlinear partial differential equations (NPDEs) in 2+1 dimensions is derived from the matrix Kadomtsev--Petviashvili equation by means of an asymptotically exact nonlinear reduction method based on Fourier expansion and spatio-temporal rescaling. The integrability by the inverse scattering method is explicitly demonstrated, by applying the reduction technique also to the Lax pair of the starting matrix equation and thereby obtaining the Lax pair for the new class of systems of equations. The characteristics of the reduction method suggest that the new systems are likely to be of applicative relevance. A reduction to a system of two interacting complex fields is briefly described.Comment: arxiv version is already officia

Broadening of the Berezinskii-Kosterlitz-Thouless transition by correlated disorder

The Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional superconductors is usually expected to be protected against disorder. However, its fingerprints in a real system, such as, e.g., the universal superfluid- density jump, are often at odds with this expectation. Here, we show that the disorder-induced granularity of the superconducting state modifies the nucleation mechanism for vortex-antivortex pairs. This leads to a considerable smearing of the universal superfluid-density jump as compared to the paradigmatic clean case, in agreement with experimental observations

BKT universality class in the presence of correlated disorder

The correct detection of the Berezinskii-Kosterlitz-Thouless (BKT) transition in quasi-two-dimensional superconductors still remains a controversial issue. Its main signatures, indeed, are often at odds with the theoretical expectations. In a recent work\cite{me} we have shown that the presence of spatially correlated disorder plays a key role in this sense being it the reason underlying the experimentally-observed smearing of the universal superfluid-density jump. In the present paper, we closely investigate the effects of correlated disorder on the BKT transition, addressing specifically the issue whether it changes or not the BKT universality class.Comment: The present paper has already been submitted as Special Issue "Proceedings of the conference SuperFluctuations 2017

Origin and genetic diversity of diploid parthenogenetic Artemia in Eurasia

There is wide interest in understanding how genetic diversity is generated and maintained in parthenogenetic lineages, as it will help clarify the debate of the evolution and maintenance of sexual reproduction. There are three mechanisms that can be responsible for the generation of genetic diversity of parthenogenetic lineages: contagious parthenogenesis, repeated hybridization and microorganism infections (e.g. Wolbachia). Brine shrimps of the genus Artemia (Crustacea, Branchiopoda, Anostraca) are a good model system to investigate evolutionary transitions between reproductive systems as they include sexual species and lineages of obligate parthenogenetic populations of different ploidy level, which often co-occur. Diploid parthenogenetic lineages produce occasional fully functional rare males, interspecific hybridization is known to occur, but the mechanisms of origin of asexual lineages are not completely understood. Here we sequenced and analysed fragments of one mitochondrial and two nuclear genes from an extensive set of populations of diploid parthenogenetic Artemia and sexual species from Central and East Asia to investigate the evolutionary origin of diploid parthenogenetic Artemia, and geographic origin of the parental taxa. Our results indicate that there are at least two, possibly three independent and recent maternal origins of parthenogenetic lineages, related to A. urmiana and Artemia sp. from Kazakhstan, but that the nuclear genes are very closely related in all the sexual species and parthenogegetic lineages except for A. sinica, who presumable took no part on the origin of diploid parthenogenetic strains. Our data cannot rule out either hybridization between any of the very closely related Asiatic sexual species or rare events of contagious parthenogenesis via rare males as the contributing mechanisms to the generation of genetic diversity in diploid parthenogenetic Artemia lineages

Studio e progetto di un sistema elettronico per il controllo di una macchina per etichettatura automatica di provette.

La tesi tratta la progettazione e realizzazione di un sistema elettronico per la gestione e controllo di un macchinario per l'etichettatura automatica di provette da laboratorio

L'utilizzo del concentrato da sangue midollare nelle pseudoartrosi diafisarie: review della letteratura e revisione della casistica.

Le pseudoartrosi rappresentano delle temibili complicanze delle fratture caratterizzate dalla mancata consolidazione della frattura dopo 6 mesi dall’evento traumatico in associazione all’assenza di segni di guarigione nei tre mesi precedenti. Il trattamento delle pseudoartrosi costituisce un reale problema per i chirurghi ortopedici a causa della refrattarietà di queste patologie verso le terapie convenzionalmente utilizzate e a causa della mancanza di linee guida esaurienti e complete che ne stabiliscano la modalità di trattamento. Negli ultimi decenni si stanno sempre più affermando terapie innovative capaci di coadiuvare i trattamenti classici al fine di migliorarne l’efficacia e di ridurre i tempi necessari per la guarigione delle pseudoartrosi. Il sempre maggiore interesse verso la medicina rigenerativa e l’ingegneria tissutale ha portato alla nascita e allo sviluppo delle terapie cellulari. Le terapie cellulari hanno come razionale quello di indurre e promuovere i processi biologici riparativi che si attivano fisiologicamente in seguito ad una frattura attraverso l’utilizzo di cellule mesenchimali multipotenti e fattori di crescita. In relazione proprio a questa attività biologica le terapie cellulari suscitano un grande interesse sia nell’ambito della ricerca che dell’utilizzo clinico. Sebbene ad oggi siano ancora agli albori della loro evoluzione, probabilmente negli anni a venire le terapie cellulari potranno rivestire un ruolo predominante nella medicina del futuro. Lo scopo di questa tesi è la valutazione dell’efficacia dell’utilizzo di cellule staminali mesenchimali con la metodica del Regenkit Extracell® BMC nel trattamento delle pseudoartrosi atrofiche delle ossa lunghe trattate nel reparto dell’Unità Operativa di Ortopedia e Traumatologia I dell’Azienda Ospedaliera Universitaria Pisana

A numerical study of planar arrays of correlated spin islands

We present our analysis of a system of interacting islands of XY spins on a triangular lattice that has been introduced a few years ago by Eley et al. to account for the phenomenology in experiments on tunable arrays of proximity coupled long superconductor-normal metal-superconductor junctions. The main features of the model are the separation of a local and a global interaction energy scale and the mesoscopic character of the spin islands. Upon lowering the temperature the model undergoes two crossovers corresponding to an increasing phase coherence on a single island and to the onset of global coherence across the array; the latter is a thermodynamical phase transition in the Ising universality class. The dependence of the second transition on the island edge-to-edge spacing is related to the proximity-effect of the coupling constant.Comment: 6 pages, 5 figures, accepted for publication in EPJ

A Nonlinear Approach for Quantum Mechanics

This work represents a possible way to achieve the Einstein-de Broglie soliton-particle concept. The weakly nonlinear Klein-Gordon equation (nonlinear quantum mechanics) is investigated by the asymptotic perturbation (AP) method for a particle confined in a box. The quantization of the energy with a slight difference with respect to the standard (linear) quantum mechanics is obtained. Both relativistic and non-relativistic cases are considered and the transition frequencies are slightly different for the linear and nonlinear quantum mechanics. Experimental verification is needed to choose between the two theories

On a Peculiar Attractor for Weakly Nonlinear Oscillators with a Two Period Quasiperiodic Forcing

We study a very peculiar nonlinear oscillator with an external two period quasiperiodic excitation, being the golden mean the ratio between the two frequencies. The two period quasi periodic forcing configuration gets an infinite frequencies number. As a consequence, we find the motion settles down in a two period quasi periodic atttractor for a wide excitation amplitude range. The competition between the two frequencies does not produce a closed curve but fills a well defined phase space region in the Poincarè section. This attractor somehow resembles strange nonchaotic attractors because both are characterized by quasiperiodic forcing. Using a suitable perturbation method, we can understand the new attractor most important characteristics and find an approximate solution for its dynamical behavior. Numerical simulations are used to check out the analytical investigation.