University of Siena

About: University of Siena is a education organization based out in Siena, Italy. It is known for research contribution in the topics: Population & Cancer. The organization has 12179 authors who have published 33334 publications receiving 1008287 citations. The organization is also known as: Università degli studi di Siena & Universita degli studi di Siena.

Isomer-specific analysis and toxic evaluation of polychlorinated biphenyls in striped dolphins affected by an epizootic in the western Mediterranean sea

Abstract: Isomer-specific concentrations of polychlorinated biphenyls (PCBs) including planar, mono- and di-ortho congeners and concentrations of DDT were determined in striped dolphins affected by a morbillivirus epizootic in the western Mediterranean in 1990. Extremely high concentrations of PCBs ranging from 94 to 670 μg/g (wet wt) were detected in the blubber. Similarly, DDT concentrations were high, between 22 and 230 μg/g (wet wt). The concentrations of three non-ortho coplanar PCBs were 43 (3,3′,4,4′-T4CB), 6.8 (3,3′,4,4′,5-P5CB), and 7.8 (3,3′,4,4′,5,5′-H6CB) ng/g (wet wt), respectively, the highest residue levels reported to date. The estimated 2,3,7,8-TCDD toxic equivalents of non-, mono- and di-ortho PCB congeners in striped dolphins were several times higher than those observed for other marine mammals and humans. Mono-ortho congeners contributed greater 2,3,7,8-TCDD toxic equivalents than non-ortho members. The higher ratio of 3,3′,4,4′,5,5′-H6CB/3,3′,4,4′,5-P5CB (IUPAC 169/126) suggested a strong induction of mixed function oxidase enzymes and highlighted the possibility of using this ratio as an index for risk assessment of PCB contamination in marine mammals. Elevated concentrations of PCBs may have played a role in the immune depression in striped dolphins, ultimately leading to the development of morbillivirus disease.

Relationships between the Tertiary structural evolution of the Sardinia-Corsica-Provençal Domain and the Northern Apennines

Abstract: Based on a revision of stratigraphic and structural data relative to the Balearic basin, the Corsica-Sardinia massif, the Northern Tyrrhenian Sea and the Northern Apennines the following new hypothesis is proposed for the area located between the Sardinian-Corsican-Provencal and Northern Apennines regions: (a) convergence with subduction of oceanic crust under the Iberian plate beginning in the Late Cretaceous; (b) continental collision in the Oligocene-Aquitanian, with development of the Northern Apennines belt and transpressive deformation in a hinterland that consisted of the Corsica-Sardinia massif (still attached to the Iberian plate); (c) in the Burdigalian the tectonic regime changed from compressive to extensional. During this period the Corsica-Sardinia massif migrated contemporaneously with opening of the Balearic basin, the Sardinian rift, and the Northern Tyrrhenian sea; (d) from the Burdigalian to the present, there was contemporaneous compression at the front and extension at the back of the Northern Apennines chain; both these features progressively migrated toward the east. The coeval extension and compression is attributed to lithospheric delamination toward the external part of the belt.

Application of Surface-Wave Methods for Seismic Site Characterization

Abstract: Surface-wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide variety of applications. A shear-wave velocity model is obtained from the solution of an inverse problem based on the surface wave dispersive propagation in vertically heterogeneous media. The analysis can be based either on active source measurements or on seismic noise recordings. This paper discusses the most typical choices for collection and interpretation of experimental data, providing a state of the art on the different steps involved in surface wave surveys. In particular, the different strategies for processing experimental data and to solve the inverse problem are presented, along with their advantages and disadvantages. Also, some issues related to the characteristics of passive surface wave data and their use in H/V spectral ratio technique are discussed as additional information to be used independently or in conjunction with dispersion analysis. Finally, some recommendations for the use of surface wave methods are presented, while also outlining future trends in the research of this topic.

Structural Insight into Potent Broad-Spectrum Inhibition with Reversible Recyclization Mechanism: Avibactam in Complex with CTX-M-15 and Pseudomonas aeruginosa AmpC β-Lactamases

Abstract: Although β-lactams have been the most effective class of antibacterial agents used in clinical practice for the past half century, their effectiveness on Gram-negative bacteria has been eroded due to the emergence and spread of β-lactamase enzymes that are not affected by currently marketed β-lactam/β-lactamase inhibitor combinations. Avibactam is a novel, covalent, non-β-lactam β-lactamase inhibitor presently in clinical development in combination with either ceftaroline or ceftazidime. In vitro studies show that avibactam may restore the broad-spectrum activity of cephalosporins against class A, class C, and some class D β-lactamases. Here we describe the structures of two clinically important β-lactamase enzymes bound to avibactam, the class A CTX-M-15 extended-spectrum β-lactamase and the class C Pseudomonas aeruginosa AmpC β-lactamase, which together provide insight into the binding modes for the respective enzyme classes. The structures reveal similar binding modes in both enzymes and thus provide a rationale for the broad-spectrum inhibitory activity of avibactam. Identification of the key residues surrounding the binding pocket allows for a better understanding of the potency of this scaffold. Finally, avibactam has recently been shown to be a reversible inhibitor, and the structures provide insights into the mechanism of avibactam recyclization. Analysis of the ultra-high-resolution CTX-M-15 structure suggests how the deacylation mechanism favors recyclization over hydrolysis.