Determinants of species susceptibility to oxidative stress: A comparison of channel catfish and brown bullhead

Xenobiotic-mediated productions of reactive oxygen species, via enzymemediated redox cycling, have been implicated in a variety of toxicological phenomena including lipid peroxidation, enzyme inactivation and oxidative DNA damage leading to cancer. A comparison was undertaken of two benthic freshwater fish species that appear to differ markedly in their susceptibility to chemical carcinogenesis—the channel catfish (Ictalurus punctatus) and the more cancer-prone brown bullhead (Ameriurus nebulosus)-in terms of basic biochemical characteristics related to oxidative stress. This has included analysis of microsomal redox cycling of model xenobiotics (e.g. menadione) as well as antioxidant and other detoxifying enzymes in hepatic tissue of the two species. In addition, endpoints of oxidative stress, such as altered glutathione status and oxidative DNA damage, were examined. These studies have revealed numerous qualitative and quantitative differences between the two species both in terms of basal enzyme activities and in species response to model prooxidants. For example, bullhead appear to possess a greater capacity for microsomal redox cycling of xenobiotics, but have glutathione-dependent defense systems less able to withstand oxidative challenge. These and other interspecific differences have allowed for an improved understanding of the basic mechanisms which may underly species susceptibility to oxidative stress and critical manifestations such as cancer.     

NADPH: Phenanthrenequinone oxidoreductase in channel catfish (Ictalurus punctatus)

The toxicity of certain polycyclic aromatic hydrocarbons has been related to the phenomenon of oxidative stress. Recent studies in our laboratory have demonstrated that 9,10-phenanthrenequinone (PQ) is an efficient redox cycling agent in cytosols of several organs of the channel catfish (Ictalurus punctatus). Stomach cytosol demonstrated a high level of dicoumarol-sensitive PQ reduction which was at least tenfold greater than that seen in kidney, liver or gill. In the presence of stomach cytosol, PQ stimulated production of Superoxide union in-vitro at rates several fold higher than did menadione, a model redox active quinone. The active component from stomach cytosol has been purified, and is termed NADPH: phenanthrenequinone oxidoreductase, which the authors believe represents a novel quinone-reducing enzyme in this species.     

Bussole ad induzione geomagnetica di tipo particolare e loro applicazioni

Riassunto L'A. descrive alcune bussole ad induzione, da lui realizzate, atte alla individuazione nello spazio di un camp magnetico debole, per es. il terrestre, o di una sua componente e delle corrispondenti direzioni. Lo scopo si raggiunge generando una f. e. m. indotta in avvolgimento (privo di nucleo) assoggettato a un flusso di induzione provocato da materiali, di conveniente permeabilità e di isteresi trascurabile, eccitati dal campo da individuarsi. L'A. pone in evidenza l'applicabilità delle bussole congegnate, sia nel campo geofisico, sia per determinazioni magnetometriche, sia per la navigazione (aerea e marittima) con descrizione di un modello particolare per la navigazione esente da effetti di variazione di inclinazione magnetica ed attualmente in corso di pratica attuazione.

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Zusammenfassung Der Verf. beschreibt einige von ihm erdachten und konstruierten Kompasse, die nach dem Prinzip der magnetischen Induktion arbeiten. Für den letzten Typen, dessen Anzeige durch die Variationen der erdmagnetischen Inklination nicht beinflusst wird, der Kompass besteht hauptsächlich aus drei völlig gleichartigen, durch einen gemeinsamen kleinen Motor angetriebenen Erdinduktoren besonderer Konstruktion, die so auf einem gemeinsamen Grundbrett angeordnet sind, dass bei einer bestimmten Orientierung des Aggregates in bezug auf die magnetische Nordsüdrichtung zwei der Induktoren entgegengesetzt gleiche Strome erzeugen, während in dem dritten Induktor in dieser Stelle kein Strom induziert wird. — Für die beschriebenen Kompasse, ausser der Verwendung in der Luftnavigation welche schon unternommen wurde, wird an verschiedenen Anwendungsmöglichkeiten hingewiesen.

     

Applicabilita' di nuove bussole alla determinazione degli elementi angolari del campo geomagnetico

Riassunto Viene dimostrata ed illustrata l'applicabilità delle bussole Giulietti alla misura della declinazione e della inclinazione geomagnetiche; esse consentono alte precisioni e sono adatte anche al pratico impiego in campagna.

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Zusammenfassung Es wird bewiesen, dass die Kompasse von Giulietti geeignet sind um die Deklination und die Inklination des geomagnetischen Feldes zu messen. Das Verfahren gestattet eine hohe Genauigkeit zu erreichen und ist auch leicht auf dem Land anwendbar.

     

Origin and emplacement of ultramafic–mafic intrusions in the Erro-Tobbio mantle peridotite (Ligurian Alps, Italy)

The Erro-Tobbio peridotites (Voltri Massif, Ligurian Alps) represent subcontinental lithospheric mantle tectonically exhumed during Permo–Mesozoic extension of the Europe–Adria lithosphere. Previous studies have shown that exhumation started during Permian times, and occurred along kilometer-scale lithospheric shear zones which enhanced progressive deformation and recrystallization from spinel- to plagioclase-facies conditions. Ongoing field and petrologic investigations have revealed that the peridotites experienced, during uplift, a composite history of diffuse melt migration and multiple episodes of ultramafic–mafic intrusions. In this paper we present the results of field, structural and petrologic–geochemical investigations into a sector of the Erro-Tobbio peridotite unit that preserves well this multiple intrusion history. Melt impregnation in the peridotites is evidenced by significant plagioclase enrichment and crystallization of unstrained orthopyroxene replacing kinked mantle olivine and clinopyroxene; impregnating melts were thus opx-saturated. Melt–rock interaction caused chemical changes in mantle minerals (e.g. Al decrease and REE increase in cpx; Ti and Cr# enrichment in spinel). Nevertheless, clinopyroxenes still exhibit LREE depletion (Ce_N/Sm_N = 0.006–0.011), indicating a depleted signature for the percolating melts. Melt impregnation was thus related to diffuse porous flow migration of depleted MORB-type melt fractions that modified their compositions towards opx saturation by mantle–melt interaction during ascent. The impregnated peridotites are intruded by a hectometer-scale stratified cumulate body, mostly consisting of troctolites and plagioclase wehrlites, showing gradational, interfingered contacts with the host mantle rocks. Subsequent intrusion events are revealed by the occurrence of olivine gabbros as decameter-wide lenses, variably thick (centimeter- to meter-scale) dykes and thin dykelets, which crosscut both the peridotite foliation and the magmatic layering in the cumulates. Overall, major and trace element compositions of minerals in the intrusives indicate that they represent variably differentiated cumulus products crystallized from rather primitive N-MORB-type aggregated melts. Slightly more evolved compositions are shown by olivine gabbros, relative to the troctolites and plagioclase wehrlites of the cumulate body. Mineral chemistry features (e.g. the Fo–An correlation and high Na, Ti, Mg# in cpx) indicate that the studied intrusive rocks crystallized at moderate pressure conditions (3–5 kbar, i.e. 9–15 km depth). Our study thus points to a progressive transition from porous flow melt migration to emplacement of magmas in fractures, presumably related to progressive change of lithospheric mantle rheology during extension-related uplift and cooling.     

Radiation Physics

Earth, Moon, and Planets -     

Gravity-Accommodated ‘Structural Wedges’ Along Thrust Ramps: A Kinematic Scheme of Gravitational Evolution

In active geodynamic areas, such as the Italian Southern Apennines, the specific structural conditions have a profound effect on both the superficial and deep gravitational evolution of slopes. Chain sectors commonly exhibit structural complexities due to the superimposition, in space and time, of diverse tectonic stress fields. In this paper, attention is focused on particular structural configurations, connected to the tectonic quaternary phases that have affected the Southern Apennines, constituting a peculiar type of lateral spread gravitational deformations – which have not been previously described.The study area is characterized by regional roughly east-verging overthrusts (Holigo–Miocene). Superimposed on these, is a system of transpressive thrust ramps (Quaternary), connected to the activity of strike-slip faults. The latest tectonic phase, still active, has been characterized by an extensional stress field, which has produced differentiated uplifts along normal faults. All these factors have encouraged an intense and widespread processes of erosion, the creation of considerable relief energy and the development of both superficial and deep gravitational phenomena.It has been ascertained that the late extensional phases favoured gravitational reactivations (with normal movements) along those most recent thrust ramps whose attitude was kinematically consistent with the main extension direction of the stress field. Such reactivations were accommodated by antithetic neo-formational structures – these are also characterized by normal kinematics. Overall, such mechanisms lead to the individuation of wedge-shaped rock portions delimited by the normally reactivated thrust ramps, on one side, and by the antithetic structures, on the other.Structural wedges represent a particular type of lateral spread phenomena. On the basis of their orientation with respect to the orography, three typical situations have been defined: (1) wedge perpendicular to the ridge; (2) wedge parallel to the ridge; (3) wedge oblique to the ridge.In this paper three Calabrian case studies, exemplifying the above-mentioned situations, are described. The same framework can be applied to sectors of chain with an analogous structural setting, for a better understanding of the kinematic features of observed gravitational phenomena.     

The evolution of the Western Ligurian Flysch Units and the role of mud diapirism in ancient accretionary prisms (Maritime Alps,Northwestern Italy)

The Western Ligurian Flysch Units represent an Upper Cretaceous to Paleogene accretionary prism overthrust onto the paleo-European continental margin during the collisional stages of the Alpine orogeny (Eocene). Their precollisional evolution has been reconsidered according to the data collected through extensive field mapping, the study of lowgrade metamorphism and by considering more strictly the processes documented in modern convergent zones.The proposed model involves chaotic facies produced by the flow of muddy sediments along decollement surfaces (diapiric melange) with the growth of mud volcanoes into an accreting wedge progressively shifting toward the European continental margin.

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Zusammenfassung Der westliche Ligurische Flysch repräsentiert die Entwicklung eines Akkretionskeiles während des Kreide-Paleogens, das auf den europäischen Kontinentalrand während der Kollisionsphase der alpidischen Orogenese (Eozän) überschoben wurde. Die Entwicklung vor der Kollision wird neu gedeutet auf der Basis ausgedehnter geologischer Felduntersuchungen, dem Studium der niedrig gradigen Metamorphose und anhand von Vergleichen mit heutigen konvergenten Zonen.Das vorgeschlagene Modell interpretiert das Erscheinen der chaotischen Fazies als Diapirismus von nur teilweise verfestigten Sedimenten und deren Umlagerung nahe Diskontinuitätsflächen im Inneren eines Akkretionprismas, das in Richtung des europäischen Kontinents wandert.

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Résumé Les flyschs de la Ligurie occidentale représentent un prisme d'accrétion du Crétacé-Paléogène charrié sur la marge continentale européenne pendant les phases de collision de l'orogenèse alpine (Eocène). Leur évolution anté-collision est reconsidérée sur la base de nouvelles données provenant du levé de terrain d'une vaste région, de l'étude du métamorphisme de degré faible et de l'application plus rigoureuse des enseignements fournis par les zones de convergence actuelles.Le modèle proposé envisage la production de facies à texture chaotique par flux diapirique de sédiments non consolidés le long de surfaces de décollement, à l'intérieur d'un prisme d'accrétion qui migre progressivement vers la marge continentale européenne.

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Frequency‐dependent multi‐offset phase analysis of surface waves: an example of high‐resolution characterization of a riparian aquifer

Multi‐offset phase analysis of seismic surface waves is an established technique for the extraction of dispersion curves with high spatial resolution and, consequently, for the investigation of the subsurface in terms of shear wave velocity distribution. However, field applications are rarely documented in the published literature. In this paper, we discuss an implementation of the multi‐offset phase analysis consisting of the estimation of the Rayleigh wave velocity by means of a moving window with a frequency‐dependent length. This allows maximizing the lateral resolution at high frequencies while warranting stability at the lower frequencies. In this way, we can retrieve the shallow lateral variability with high accuracy and, at the same time, obtain a robust surface‐wave velocity measurement at depth. In this paper, we apply this methodology to a dataset collected for hydrogeophysical purposes and compare the inversion results with those obtained by using refraction seismics and electrical resistivity tomography. The surface‐wave results are in good agreement with those provided by the other methods and demonstrate a superior capability in retrieving both lateral and vertical velocity variations, including inversions. Our results are further corroborated by the lithological information from a borehole drilled on the acquisition line. The availability of multi‐offset phase analysis data also allows disentangling a fairly complex interpretation of the other geophysical results.