Excitations of metastable superfluid 4He at pressures up to 40 bars.

Neutron scattering measurements of the fundamental excitations of liquid 4He confined in 44 A pore diameter gelsil glass at pressures up to 40 bars in the wave vector range 0.41.6 A(-1), especially the rotons, are observed up to complete solidification of all the liquid at a pressure of approximately 40 bars where the roton vanishes. At and above a pressure of 35.1 bars, Bragg peaks are observed, indicating coexistence of liquid and solid in the pores at pressures 35 less than or approximately equal P less than or approximately equal 40 bars.

Dynamics of quantum liquids in confinement, theory and experiment.

Liquid (4)He immersed in porous media such as aerogel, Vycor, and Geltech silica are excellent examples of bosons in disorder and confinement. Of special interest is the impact of disorder on Bose-Einstein condensation (BEC), on the elementary excitations of the superfluid and on their connection to the superfluid properties. Indeed, the modifications induced by disorder can be used to reveal the interdependence of BEC, the excitations and superfluidity. To date, the superfluid properties in porous media are much more completely documented than BEC or the excitations. In this paper, we review measurements of the excitations by neutron scattering, focusing particularly on their temperature dependence and the existence of phonon-roton excitations at higher temperatures. The weight of single excitation response at higher temperatures suggests the existence of localized BEC above the superfluid-normal transition temperature in porous media. We sketch several recent predictions made for BEC, the excitations, and the superfluid properties in disorder. Connections with other "Dirty Bose systems" are made.

Observation of a new excitation in bcc 4He by inelastic neutron scattering.

We report neutron-scattering measurements of the phonons in bcc solid 4He. In general, only three acoustic phonon branches should exist in a monatomic cubic crystal. In addition to these phonon branches, we found a new "opticlike" mode along the [110] direction. One possible interpretation of this new mode is in terms of localized excitations unique to a quantum solid.

Hepatitis B virus Dane particles bind to human plasma apolipoprotein H.

Human apolipoprotein H (apo H) was found to bind specifically to hepatitis B surface antigen (HBsAg) from hepatitis B virus (HBV)-infected individuals. We used recombinant HBsAg proteins to analyze HBV domains recognized by apo H. We showed that the myristylated pre-S1 domain of HBsAg strongly interacted with apo H. This binding involved phospholipid components of the HBV envelope because their removal by detergent prevented apo H-HBsAg interaction. The opposite effects of iron and zinc metal ions on binding suggest that the oxidation of phospholipids also affects apo H-HBsAg interaction. After fractionation of viral particles on a sucrose gradient, and their addition to microtiter plates coated with apo H or anti-HBsAg, we observed that the maximal anti-HBsAg capture activity corresponded to a sucrose concentration of 36%, whereas the maximal apo H capture activity corresponded to a concentration of 39%. Electron microscopy and polymerase chain reaction (PCR) Southern blot studies of these fractions showed that the fraction with maximal apo H binding predominantly contained full Dane particles. Finally, we studied apo H-HBsAg binding relative to the presence of hepatitis B virus markers and observed that apo H binding activity for HBsAg was higher in sera from patients in the active virus replication phase.

Quantum impurities and the neutron resonance peak in YBa2Cu3O7: Ni versus Zn.

The influence of magnetic (S=1) and nonmagnetic (S=0) impurities on the spin dynamics of an optimally doped high temperature superconductor is compared in YBa2(Cu0.97Ni0.03)3O7 (Tc=80 K) and YBa2(Cu0.99Zn0.01)3O7 (Tc=78 K). In the Ni-substituted system, the magnetic resonance peak (which is observed at Er approximately 40 meV in the pure system) shifts to lower energy with a preserved Er/Tc ratio while the shift is much smaller upon Zn substitution. By contrast Zn, but not Ni, restores significant spin fluctuations around 40 meV in the normal state. These observations are discussed in the light of models proposed for the magnetic resonance peak.

The spin excitation spectrum in superconducting YBa(2)Cu(3)O(6.85)

A comprehensive inelastic neutron scattering study of magnetic excitations in the near optimally doped high-temperature superconductor YBa(2)Cu(3)O(6.85) is presented. The spin correlations in the normal state are commensurate with the crystal lattice, and the intensity is peaked around the wave vector characterizing the antiferromagnetic state of the insulating precursor, YBa(2)Cu(3)O(6). Profound modifications of the spin excitation spectrum appear abruptly below the superconducting transition temperature T(c), where a commensurate resonant mode and a set of weaker incommensurate peaks develop. The data are consistent with models that are based on an underlying two-dimensional Fermi surface, predicting a continuous, downward dispersion relation connecting the resonant mode and the incommensurate excitations. The magnetic incommensurability in the YBa(2)Cu(3)O(6+)(x) system is thus not simply related to that of another high-temperature superconductor, La(2-)(x)Sr(x)CuO(4), where incommensurate peaks persist well above T(c). The temperature-dependent incommensurability is difficult to reconcile with interpretations based on charge stripe formation in YBa(2)Cu(3)O(6+x) near optimum doping.

Organization of the large mitochondrial genome in the isopod Armadillidium vulgare.

The mitochondrial DNA (mtDNA) in animals is generally a circular molecule of approximately 15 kb, but there are many exceptions such as linear molecules and larger ones. RFLP studies indicated that the mtDNA in the terrestrial isopod Armadillidium vulgare varied from 20 to 42 kb. This variation depended on the restriction enzyme used, and on the restriction profile generated by a given enzyme. The DNA fragments had characteristic electrophoretic behaviors. Digestions with two endonucleases always generated fewer fragments than expected; denaturation of restriction profiles reduced the size of two bands by half; densitometry indicated that a number of small fragments were present in stoichiometry, which has approximately twice the expected concentration. Finally, hybridization to a 550-bp 16S rDNA probe often revealed two copies of this gene. These results cannot be due to the genetic rearrangements generally invoked to explain large mtDNA. We propose that the large A. vulgare mtDNA is produced by the tripling of a 14-kb monomer with a singular rearrangement: one monomer is linear and the other two form a circular dimer. Densitometry suggested that these two molecular structures were present in different proportions within a single individual. The absence of mutations within the dimers also suggests that replication occurs during the monomer phase.

Isolation of Multiple Subspecies of Bacillus thuringiensis from a Population of the European Sunflower Moth, Homoeosoma nebulella.

Five subspecies of Bacillus thuringiensis were isolated from dead and diseased larvae obtained from a laboratory colony of the European sunflower moth, Homoeosoma nebulella. The subspecies isolated were B. thuringiensis subspp. thuringiensis (H 1a), kurstaki (H 3a3b3c), aizawai (H 7), morrisoni (H 8a8b), and thompsoni (H 12). Most isolates produced typical bipyramidal crystals, but the B. thuringiensis subsp. thuringiensis isolate produced spherical crystals and the B. thuringiensis subsp. thompsoni isolate produced a pyramidal crystal. Analysis of the parasporal crystals by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the crystals from the B. thuringiensis subsp. kurstaki and aizawai isolates contained a protein of 138 kDa whereas those from B. thuringiensis subsp. morrisoni contained a protein of 145 kDa. The crystals from B. thuringiensis subsp. thuringiensis contained proteins of 125, 128, and 138 kDa, whereas those from B. thuringiensis subsp. thompsoni were the most unusual, containing proteins of 37 and 42 kDa. Bioassays of purified crystals conducted against second-instar larvae of H. nebulella showed that the isolates of B. thuringiensis subspp. aizawai, kurstaki, and thuringiensis were the most toxic, with 50% lethal concentrations (LC(inf50)s) of 0.15, 0.17, and 0.26 (mu)g/ml, respectively. The isolates of B. thuringiensis subspp. morrisoni and thompsoni had LC(inf50)s of 2.62 and 37.5 (mu)g/ml, respectively. These results show that a single insect species can simultaneously host and be affected by a variety of subspecies of B. thuringiensis producing different insecticidal proteins.

Incorporation of pseudorabies virus gD into human immunodeficiency virus type 1 Gag particles produced in baculovirus-infected cells.

The human immunodeficiency virus type 1 (HIV-1) Pr55gag precursors were previously shown to assemble and bud efficiently as noninfectious virus-like particles (VLPs) when expressed in baculovirus-infected insect cells. In this study, we examined the abilities of foreign antigens to be incorporated on the outer surface of HIV-1 Gag particles. We have used a dual recombinant baculovirus, expressing the HIV-1 Gag gene and gD gene under the control of the P10 and polyhedrin promoters, respectively, to obtain hybrid VLPs. Transmission electron microscopy of insect cells infected with the dual recombinant revealed very large aggregates of particles budding from the cell membrane. The release of VLPs into the culture medium was clearly different for a recombinant baculovirus producing solely HIV-1 Gag, for which particles were uniformly distributed all around the cell surface. Biochemical analysis of hybrid particles indicated that glycoprotein gD was packaged into HIV-1 Gag VLPs. Moreover, the carboxy-terminal p6 region of Gag polyprotein and the glycoprotein gD intracytoplasmic domain were not required for gD incorporation. The experiments described here clearly demonstrate that glycoprotein gD can be packaged with HIV-1 Gag particles and released from insect cells.

Biochemical characterization of Drosophila melanogaster acetylcholinesterase expressed by recombinant baculoviruses.

Recombinant baculoviruses expressing full length and 3' truncated forms of c-DNA encoding the Drosophila melanogaster acetylcholinesterase (AChE) were constructed. Biochemical analyses showed that full length recombinant protein was enzymatically active and anchored to the cell membrane via a glycolipidic residue. DTT treatment dissociated the native form into monomers migrating as did the corresponding form of AChE extracted from drosophila heads. Finally, DFP labelling demonstrated that the specific proteolytic cleavage leading to the formation of 55 and 16 kDa subunits occurred in Sf9 cells. In contrast with the full-length enzyme, C-terminal-truncated forms were highly secreted, confirming the prominent role of the C-terminal hydrophobic peptide for the addition of the glycolipidic residue. Accumulation of inactive precursor was observed when recombinant proteins were overproduced using an improved baculovirus, suggesting a saturation of insect cell machineries.

Morphological and genomic characterization of two reoviruses (P and W2) pathogenic for marine crustaceans; do they constitute a novel genus of the Reoviridae family?

P and W2 viruses are pathogenic in two crustaceans of the Mediterranean Sea, Macropipus depurator and Carcinus mediterraneus, respectively. Investigation of virus, virus density and genome structure leads us to propose their classification in a genus similar to aquareovirus of the Reoviridae family. They differ from aquareoviruses by the number of dsRNA segments forming the genome (12 instead of 11), their electrophoretic pattern in PAGE (1/5/6 instead of 3/3/5), and the absence of virus replication in fish cell lines.

[Female urinary stress incontinence and insufficient closing pressures. Results of perineal sphincter electromyography]. / Incontinence urinaire d'effort féminine et insuffisance des pressions de clôture. Que peut-on attendre de l'électromyographie des sphincters périneaux?

Prior to a clinical evaluation of the efficacy of sphincter and perineal rehabilitation in female urinary stress incontinence due to striated sphincter incompetence, and in order to define the cause, 32 patients with stress incontinence with very low urethral closing pressure on urodynamic studies, underwent a perineal electromyographic investigation Three types of sphincteric lesion were detected: an isolated lesion of the striated muscle fibres, an isolated neurogenic lesion of the internal pudendal nerve and a neurogenic lesion of the internal pudendal nerve in a context of sensorimotor polyneuropathy.

Isolation and characterization of a RNA-virus like particle from Candida curvata.

A virus-like particle (VLP) of 35 nm diameter has been isolated from the lipolytic yeast Candida curvata. The VLP contains a linear, double stranded RNA molecule of 1.55 microns in length.