Protein secondary structure assignment through Voronoï tessellation.

We present a new automatic algorithm, named VoTAP (Voronoï Tessellation Assignment Procedure), which assigns secondary structures of a polypeptide chain using the list of alpha-carbon coordinates. This program uses three-dimensional Voronoï tessellation. This geometrical tool associates with each amino acid a Voronoï polyhedron, the faces of which unambiguously define contacts between residues.

Impeded growth of magnetic flux bubbles in the intermediate state pattern of type I superconductors.

Normal state bubble patterns in type I superconducting indium and lead slabs are studied by the high resolution magneto-optical imaging technique. The size of bubbles is found to be independent of the long-range interaction between the normal state domains. Under bubble diameter and slab thickness proper scaling, the results gather onto a single master curve.

Lymphoid aggregates in gonads of embryos, hatchlings, and young of turtles with temperature-dependent sex determination.

Cellular infiltrations forming lymphoid-like aggregates were previously observed in gonads of two turtle species exhibiting temperature-dependent sex determination (TSD): at hatching in Chelydra serpentina; at and after hatching in Emys orbicularis. We show here that such aggregates are also present in gonads of Testudo graeca by the end of embryonic development, suggesting that their occurrence is general in turtles. Since in C.

Alternative morphs and plasticity of vulval development in a rhabditid nematode species.

The nematode species Rhabditis sp. SB347 (Family Rhabditidae) in standard culture conditions displays two developmental morphs with distinct modes of sexual reproduction: (1). females and males that develop through four feeding juvenile ("larval") stages; (2).

High mutation rate of TPE repeats: a microsatellite in the putative transposase of the hobo element in Drosophila melanogaster.

The hobo transposable element contains a polymorphic microsatellite sequence located in its coding region, the TPE repeats. Previous surveys of natural populations of Drosophila melanogaster have detected at least seven different hobo transposons. These natural populations are geographically structured with regard to TPE polymorphism, and a scenario has been proposed for the invasion process.

[Cell polarity and oocyte determination in Drosophila melanogaster].

During early oogenesis, one cell from a cyst of 16 germ cells is selected to become the oocyte. Recent data suggest that the choice of this cell within the cyst is strongly biased as early as the cyst itself forms. However, it was further shown that, although selected, the oocyte fate needs to be maintained.

Degree of sex reversal as related to plasma steroid levels in genetic female chickens (Gallus domesticus) treated with Fadrozole.

The objectives of this work were to determine whether or not plasma levels of testosterone and estradiol reflect the various grades of sex reversal in genetic female chickens treated with Fadrozole (CGS 16949 A), a nonsteroidal aromatase inhibitor, and whether gonadal aromatase activity and plasma levels of testosterone and estradiol in treated females can or not be modified by post-hatch treatments with Fadrozole or Fadrozole + testosterone. Eggs were injected with 1 mg Fadrozole on day 4 of incubation. In females having developed sex-reversed gonads, endocrine parameters (estradiol and testosterone) at and after 13 weeks of age were indicative of the degree of sex reversal, with, for example, sex-reversed females with two testes having the highest levels of testosterone and the lowest levels of estradiol.

Telomeric associated sequences of Drosophila recruit polycomb-group proteins in vivo and can induce pairing-sensitive repression.

In Drosophila, relocation of a euchromatic gene near centromeric or telomeric heterochromatin often leads to its mosaic silencing. Nevertheless, modifiers of centromeric silencing do not affect telomeric silencing, suggesting that each location requires specific factors. Previous studies suggest that a subset of Polycomb-group (PcG) proteins could be responsible for telomeric silencing.

Telomeric transgenes and trans-silencing in Drosophila.

Autonomous P elements, inserted in heterochromatic telomeric associated sequences (TAS) at the X chromosome telomere (site 1A) have strong P element regulatory properties that include repression of P-induced hybrid-dysgenesis and of P-lacZ expression in the germline. P-lacZ insertions or defective P elements at 1A in TAS can also repress in trans a euchromatic P-lacZ in the germline. This property has been called a trans-silencing effect (TSE).

Topological order in the insulating Josephson junction array.

We propose a Josephson junction array which can be tuned into an unconventional insulating state by varying external magnetic field. This insulating state retains a gap to half-vortices; as a consequence, such an array with nontrivial global geometry exhibits a ground state degeneracy. This degeneracy is protected from the effects of external noise.

The evolution of autosomal suppressors of sex-ratio drive in Drosophila simulans.

Sex-ratio drive, which results in males siring female-biased progeny, has been reported in several Drosophila species, including D. simulans. It is caused by X-linked drivers that prevent the production of Y-bearing sperm.

Control of vulval competence and centering in the nematode Oscheius sp. 1 CEW1.

To compare vulva development mechanisms in the nematode Oscheius sp. 1 to those known in Caenorhabditis elegans, we performed a genetic screen for vulva mutants in Oscheius sp. 1 CEW1.

P element-encoded regulatory products enhance Repeat-Induced Gene Silencing (RIGS) of P-lacZ-white clusters in Drosophila melanogaster.

In Drosophila melanogaster, some clusters of P transgenes ( P-lacZ-white) display a variegating phenotype for the white marker in the eye, a phenomenon termed "Repeat-Induced Gene Silencing" (RIGS). We have tested the influence of the P element repression state (P cytotype) on the eye phenotype of several P-lac-w clusters that differ in transgene copy number or genomic insertion site. P element-encoded regulatory products strongly enhance RIGS.

Evolution of Wolbachia-induced cytoplasmic incompatibility in Drosophila simulans and D. sechellia.

The intracellular bacterium Wolbachia invades arthropod host populations through various mechanisms, the most common of which being cytoplasmic incompatibility (CI). CI involves elevated embryo mortality when infected males mate with uninfected females or females infected with different, incompatible Wolbachia strains. The present study focuses on this phenomenon in two Drosophila species: D.

Rapsyn escorts the nicotinic acetylcholine receptor along the exocytic pathway via association with lipid rafts.

The 43 kDa receptor-associated protein rapsyn is a myristoylated peripheral protein that plays a central role in nicotinic acetylcholine receptor (AChR) clustering at the neuromuscular junction. In a previous study, we demonstrated that rapsyn is specifically cotransported with AChR via post-Golgi vesicles targeted to the innervated surface of the Torpedo electrocyte (Marchand et al., 2000).

Adsorption in noninterconnected pores open at one or at both ends: a reconsideration of the origin of the hysteresis phenomenon.

We report on an experimental study of adsorption isotherm of nitrogen onto porous silicon with noninterconnected pores open at one or at both ends in order to check for the first time the old (1938) but always current idea based on Cohan's description which suggests that the adsorption of gas should occur reversibly in the first case and irreversibly in the second one. Hysteresis loops, the shape of which is usually associated with interconnections in porous media, are observed whether the pores are open at one or at both ends, in contradiction with Cohan's model.

Axonemal activity relative to the 2D/3D-waveform conversion of the flagellum.

The waveform of the flagellum of the sea urchin spermatozoon is mainly planar, but its 3D-properties were evoked for dynamic reasons and described as helical. In 1975, the apparent twisting pattern of the sea urchin axoneme was described [Gibbons I. 1975.

Self-healing slip pulses along a gel/glass interface.

We present experimental evidence of self-healing shear cracks at a gel/glass interface. This system exhibits two dynamical regimes depending on the driving velocity: steady sliding at high velocity (>V(c) approximately 100--125 microm/s), characterized by a shear-thinning rheology, and periodic stick-slip dynamics at low velocity. In this last regime, slip occurs by propagation of pulses that restick via a "healing instability" occurring when the local sliding velocity reaches the macroscopic transition velocity V(c).

Measuring surface stress discontinuities in self-organized systems with X rays.

We have performed a grazing incidence x-ray diffraction study of the self-organized N/Cu(001) system. Diffraction satellites associated with self-organization are particularly intense around Bragg conditions of the bulk crystal. Bulk elastic relaxations due to surface stress discontinuities at domain boundaries are responsible for this feature.

P-Element repression in Drosophila melanogaster by variegating clusters of P-lacZ-white transgenes.

In Drosophila, clusters of P transgenes (P-lac-w) display a variegating phenotype for the w marker. In addition, X-ray-induced rearrangements of chromosomes bearing such clusters may lead to enhancement of the variegated phenotype. Since P-lacZ transgenes in subtelomeric heterochromatin have some P-element repression abilities, we tested whether P-lac-w clusters also have the capacity to repress P-element activity in the germline.

Sex reversal and aromatase in chicken.

Aromatase inhibitors administered before sexual differentiation of the gonads can induce sex reversal in female chickens. To analyze the process of sex reversal, we have followed for several months the changes induced by Fadrozole, a nonsteroidal aromatase inhibitor, in gonadal aromatase activity and in morphology and structure of the female genital system. Fadrozole was injected into eggs on day four of incubation, and its effects were examined during the embryonic development and for eight months after hatching.

Immunolocalization of HP1 proteins in metaphasic mammalian chromosomes.

HP1 proteins are conserved non histone chromosomal proteins involved in the epigenetic repression of transcription. Three HP1 proteins, HP1alpha, HP1beta and HP1gamma are expressed in mammalian cells. Polyclonal antibodies directed against peptides specific for HP1alpha and HP1gamma were elicited in rabbits, affinity purified, then used to localize both proteins on spreads of unfixed metaphasic chromosomes.

Jamming creep of a frictional interface.

We measure the displacement response of a frictional multicontact interface between identical polymer glasses to a biased shear force oscillation. We evidence the existence, for maximum forces close below the nominal static threshold, of a jamming creep regime governed by an aging-rejuvenation competition acting within the micrometer-sized contacting asperities. The time dependence of the creep process deviates from the standard Rice-Ruina [J.