The expression of CYP1A,vitellogenin and zona radiata proteins in Atlantic salmon (Salmo salar) after oral dosing with two commercial PBDE flame retardant mixtures: absence of short-term responses

The short-term effects of the commercial PBDE flame retardant mixtures Penta-BDE and cta-BDE on the expression of cytochrome P450 1A (CYP1A), vitellogenin (Vtg) and zona radiata proteins (Zrp) were investigated in juvenile salmon (Salmo salar). For this purpose, groups of fish were dosed twice (oral intake at days I and 4) with 10 and 50 mg/kg body weight of both commercial mixtures. The fishes were sacrificed at day 7 (n = 5 for each group) and 14 (n = 6 for each group), and blood, liver, fillet, and brain were collected. Blanks and positive controls were also part of the experiment. The expressions of Vtg, Zrp, and CYPIA were measured with several techniques (EROD, ELISA, Western, Northern and Slot Blot). The values in the groups of fish treated with Penta-BDE or Octa-BDE did not significantly differ from the reference group for any of the parameters tested. In contrast, the positive control groups treated with estradiol-17beta for Vtg and Zrp expression, and beta-naphthoflavone for CYP1A expression did show a significant response, indicating the potential sensitivity of the fishes for the parameters measured. Since the results of the chemical analyses showed concentrations of a number of PBDE congeners in liver, fillet, and brain that were about three orders of magnitude above those of fish from the North Sea, it is concluded that the short-term toxicity of both commercial PBDE mixtures for these endpoints was low.     

Development of two novel CYP-antibodies and their use in a PCB exposure experiment with Mytilus edulis

In an attempt to learn more about the cytochrome P450 (CYP) system of mussels, we used protein databases and alignment software to extract highly conserved CYP sequences. From these alignments synthetic peptides were produced and used for rabbit immunisation, which yielded polyclonal antibodies against the CYP families 2 and 4. The antibodies were evaluated with Western Blot and ELISA assays, using digestive gland microsomal samples from the mussel Mytilus edulis. Western Blots revealed immunoreactions for both antibodies. The anti-CYP2 sequence rendered one major immunopositive protein of approximately 49 kDa size, and weak signals for proteins of approximately 41 and 56 kDa size. The anti-CYP4 sequence rendered two major bands of approximately 56 and 59 kDa size, and also a weak immunoreaction with a protein of approximately 43 kDa size. ELISA rendered only weak signals even with a 1:50 dilution of IgG-purified serum. A 10-day exposure to Aroclor 1254 did not appear to affect any of the immunopositive proteins, while total PCBs in soft bodies increased from 14-40 ng/g DW in controls to 373-638 ng/g DW in exposed mussels.     

Gas hydrate disturbance fabrics of southern Hydrate Ridge sediments (ODP Leg 204): Relationship with texture and physical properties

Soupy and mousse-like fabrics are disturbance sedimentary features that result from the dissociation of gas hydrate, a process that releases water. During the core retrieval process, soupy and mousse-like fabrics are produced in the gas hydrate-bearing sediments due to changes in pressure and temperature conditions. Therefore, the identification of soupy and mousse-like fabrics can be used as a proxy for the presence of gas hydrate in addition to other evidence, such as pore water freshening or anomalously cool temperature. We present here grain-size results, mineralogical composition and magnetic susceptibility data of soupy and mousse-like samples from the southern Hydrate Ridge (Cascadia accretionary complex) acquired during Leg 204 of the Ocean Drilling Program. In order to study the relationship between sedimentary texture and the presence of gas hydrates, we have compared these results with the main textural and compositional data available from the same area. Most of the disturbed analyzed samples from the summit and the western flank of southern Hydrate Ridge show a mean grain size coarser than the average mean grain size of the hemipelagic samples from the same area. The depositional features of the sediments are not recognised due to disturbance. However, their granulometric statistical parameters and distribution curves, and magnetic susceptibility logs indicate that they correspond to a turbidite facies. These results suggest that gas hydrates in the southern Hydrate Ridge could form preferentially in coarser grain-size layers that could act as conduits feeding gas from below the BSR. Two samples from the uppermost metres near the seafloor at the summit of the southern Hydrate Ridge show a finer mean grain-size value than the average of hemipelagic samples. They were located where the highest amount of gas hydrates was detected, suggesting that in this area the availability of methane gas was high enough to generate gas hydrates, even within low-permeability layers. The mineralogical composition of the soupy and mousse-like sediments does not show any specific characteristic with respect to the other samples from the southern Hydrate Ridge.     

Seismic analyses of Cenozoic contourite drift development in the Northern Norwegian Sea

Four drift accumulations have been identified on the continental margin of northern Norway; the Lofoten Drift, the Vesterålen Drift, the Nyk Drift and the Sklinnadjupet Drift. Based on seismic character these drifts were found to belong to two main groups; (1) mounded, elongated, upslope accretion drifts (Lofoten Drift, Vesterålen Drift and Nyk Drift), and (2) infilling drifts (Sklinnadjupet Drift). The drifts are located on the continental slope. Mainly surface and intermediate water circulation, contrary to many North Atlantic and Antarctic drifts that are related to bottom water circulation, and sediment availability have controlled their growth. Sediments were derived both from winnowing of the shelf and upper slope and from ice sheets when present on the shelf. The main source area was the Vøring margin. This explains the high maximum average sedimentation rate of the nearby Nyk (1.2 m/ka) and Sklinnadjupet (0.5 m/ka) Drifts compared with the distal Lofoten (0.036 m/ka) and Vesterålen (0.060 m/ka) Drifts. The high sedimentation rate of the Nyk Drift, deposited during the period between the late Saalian and the late Weichselian is of the same order of magnitude as previously reported for glacigenic slope sediments deposited during glacial maximum periods only. The Sklinnadjupet Drift is infilling a paleo-slide scar. The development of the infilling drift was possible due to the available accommodation space, a slide scar acting as a sediment trap. Based on the formation of diapirs originating from the Sklinnadjupet Drift sediments we infer these sediments to have a muddy composition with relatively high water content and low density, more easily liquefied and mobilised compared with the glacigenic diamictons.     

Seasonal dynamics of elemental sulfur in two coastal sediments

A spectrophotometric method for elemental sulfur (S⁰) analysis without interference from other reduced sulfur compounds was adapted for the use in reducing sediments. The S⁰ distribution in two coastal sediments was studied regularly from summer to winter and compared to factors regulating the S⁰ accumulation, such as redox potentials, the rate of bacterial sulfide production and the general sulfur chemistry. Dense coatings of sulfur bacteria developed on the sediment surface of a sulfuretum which had an S⁰ concentration of up to 41 μmol S cm^?3. The 2·5-mm thick bacterial coating contained 40% of all S⁰ in the sediment. A more typical marine sediment with a few cm thick oxidized surface layer had an S⁰ maximum of 1–3 μmol S cm^?3 at 2–4 cm depth. The S⁰ maximum in both sediments increased from summer to winter as the sediments gradually became more oxidized. The deeper layers maintained a low S⁰ concentration. Most of the S⁰ in the upper few mm of a laboratory sulfuretum was present inside sulfur bacteria and actively migrated up and down with the bacteria depending upon the changing light and oxygen conditions.     

Weak-contrast approximation of the elastic scattering matrix in anisotropic media

The plane-wave reflection and transmission coefficients at a plane interface between two anisotropic media constitute the elements of the elastic scattering matrix. For a 1-D anisotropic medium the eigenvector decomposition of the system matrix of the transformed elasto-dynamic equations is used to derive a general expression for the scattering matrix. Depending on the normalization of the eigenvectors, the expressions give scattering coefficients for amplitudes or for vertical energy flux.Computing the vertical slownesses and the corresponding polarizations, the eigenvector matrix and its inverse can be found. We give a simple formula for the inverse, regardless of the normalization of the eigenvectors. When the eigenvectors are normalized with respect to amplitudes of displacement (or velocity), the calculation of the scattering matrix for amplitudes is simplified.When the relative changes in all parameters are small, a weak-contrast approximation of the scattering matrix, based on the exactly determined polarization vectors in an average medium, is obtained. The same approximation is also derived directly from the transformed elasto-dynamic equations for a smooth vertically inhomogeneous medium, proving the consistency of the approximation.For monoclinic media, with the mirror symmetry plane parallel to the interface, the approximative scattering matrix is given in terms of analytic expressions for the non-normalized eigenvectors and vertical slownesses. For transversely isotropic media with a vertical axis of symmetry (VTI) and isotropic media, explicit solutions for the weak-contrast approximations of the scattering matrices have been obtained. The scattering matrix for amplitudes for isotropic media is well known. The scattering matrix for vertical energy flux may have applications in AVO analysis and inversion due to the reciprocity of the reflection coefficients for converted waves.Numerical examples for monoclinic and VTI media provide good agreement between the approximative and the exact reflection matrices. It is, however, expected that the approximations cannot be used when the symmetry properties of the two media are very different. This is because the approximation relies on a small relative contrast between the eigenvectors in the two media.Presented at the Workshop Meeting on Seismic Waves in Laterally Inhomogeneous Media, Castle of Trest, Czech Republic, May 22–27, 1995.     

Solar noise storms coordinated observations: May 16–24, 1981

We present the main results obtained from the coordinated observations of solar radio noise storms organized by C.E.S.R.A. in May 1981. They concern the structure and polarization of radio sources, and the relation with the photospheric magnetic field. A model of coronal magnetic field, accounting for the observations, is briefly discussed.     

Close binary systems before and after mass transfer: A comparison of observations and theory

From a search through the literature 174 close binaries with known absolute dimensions have been sampled. Distinction is made between systems before and after mass exchange. Mass, period and mass ratio distributions and relations of the group of unevolved binaries (i.e., prior to mass exchange) are transformed into corresponding distributions and relations of evolved binaries. The transformations are based upon theM _1f=g(M _1f) relation derived from an extended set of published theoretical computations of the evolution of close binaries. From this relation the following characteristics of the system after mass exchange are computed:M _1f,M _2f (andq _f),P _f. Five different modes of mass transfer were applied for the computation of the values ofP _f andM _2f. The variation of the period was calculated using the formalism given by Vanbeverenet al. (1979). The results are compared to the observations of binary systems after mass exchange, and are discussed together with an analysis of the effect of several selection effects present in the distributions. The main conclusion is that, during mass exchange in close binaries, more than 50% of the mass is lost to the system in the process of transfer, removing a large amount of angular momentum.This research is supported by the National Foundation of Collective Fundamental Research of Belgium (F.K.F.O.) under No. 2.9009.79.     

A model of the origin of the Jovian ring

Starting with the assumption that the micron-sized particles which make up the bright Jovian ring are fragments of erosive collisions between micrometeoroid projectiles and large parent bodies, a physical model of the ring is calculated. The physics of high-velocity impacts leads to a well-defined size distribution for the ejecta, the optical properties of which can be compared with observation. This gives information on the ejecta material (very likely silicates) and on the maximum size of the projectiles, which turns out to be about 0.1 μm. The origin of these projectiles is discussed, and it is concluded that dust particles ejected in volcanic activity from Io are the most likely source. The impact model leads quite naturally to a distribution in ejecta sizes, which in turn determines the structure of the ring. The largest ejecta form the bright ring, medium-sized ejecta form a disk extending all the way to the Jovian atmosphere, and the small ejecta form a faint halo, the structure of which is dominated by electromagnetic forces. In addition to the Io particles, interaction with interplanetary micrometeoroids is also considered. It is concluded that μm-sized ejecta from this source have ejection velocities which are several orders of magnitude too large, and thus cannot contribute significantly to the observed bright ring. However, the total mass ejection rate is significant. Destruction of these ejecta by the Io particles may provide additional particles for the halo.     

The ion-composition of the plasma produced by impacts of fast dust particles

The composition of the impact plasma produced by fast dust particles (v > 1 km/sec) hitting an Au or W target was measured both with a model of the HELIOS micrometeoroid experiment (low electric field at the target) and a high field detector. The plasma composition and the total plasma charge depend strongly on the impact velocity and the electric field strength at the target. Spectra of 9 different projectile-target combinations were analysed. Two types of spectra could be observed, depending on the projectile material. (1) Spectra of metals and hard dielectrics (Mohs' hardness ? 5). Particle constituents of low ionisation energy (e · u ? 7eV, e.g. Na, K, Al) dominate the spectra of these materials at impact velocities below 10 km/sec. At higher speed the relative intensities change and new ions with higher ionisation energies appear. (2) Spectra of soft dielectrics (Mohs' hardness < 3). Below 9 km/sec these materials produced less total charge than did the others. The highest masses were detected at 74 amu. The relative abundance of ions with low ionization energies such as Li, Na, K, etc. is comparatively small. Negative ions were also observed in the impact plasma. Their total number was found to be approximately 3–6% of that of the positive ions at 6 km/sec particle speed.