Ant-based swarming with positionless micro air vehicles for communication relay

Swarming without positioning information is interesting in application-oriented systems because it alleviates the need for sensors which are dependent on the environment, expensive in terms of energy, cost, size and weight, or unusable at useful ranges for real-life scenarios. This principle is applied to the development of a swarm of micro air vehicles (SMAVs) for the deployment of ad hoc wireless communication networks (SMAVNETs) between ground users in disaster areas. Rather than relying on positioning information, MAVs rely on local communication with immediate neighbors and proprioceptive sensors which provide heading, speed and altitude. To solve the challenging task of designing agent controllers to achieve the swarm behavior of the SMAVNET, inspiration is taken from army ants which are capable of laying and maintaining pheromone paths leading from their nest to food sources in nature. This is analogous to the deployment of communication pathways between multiple ground users. However, instead of being physically deposited in the air or on a map, pheromone is virtually deposited on the MAVs using local communication. This approach is investigated in 3D simulation in a simplified scenario with two ground users.     

A genome scan for quantitative trait loci affecting the Salmonella carrier-state in the chicken

Selection for increased resistance to Salmonella colonisation and excretion could reduce the risk of foodborne Salmonella infection. In order to identify potential loci affecting resistance, differences in resistance were identified between the N and 6₁ inbred lines and two QTL research performed. In an F2 cross, the animals were inoculated at one week of age with Salmonella enteritidis and cloacal swabs were carried out 4 and 5 wk post inoculation (thereafter called CSW4F2 and CSW4F2) and caecal contamination (CAECF2) was assessed 1 week later. The animals from the (N × 6₁) × N backcross were inoculated at six weeks of age with Salmonella typhimurium and cloacal swabs were studied from wk 1 to 4 (thereafter called CSW1BC to CSW4BC). A total of 33 F₂ and 46 backcross progeny were selectively genotyped for 103 and 135 microsatellite markers respectively. The analysis used least-squares-based and non-parametric interval mapping. Two genome-wise significant QTL were observed on Chromosome 1 for CSW2BC and on Chromosome 2 for CSW4F2, and four suggestive QTL for CSW5F2 on Chromosome 2, for CSW5F2 and CSW2BC on chromosome 5 and for CAECF2 on chromosome 16. These results suggest new regions of interest and the putative role of SAL1.     

Altitudinal variation in fertility and vegetative growth in the invasive plant Rubus alceifolius Poiret (Rosaceae), on Réunion island.

Rubus alceifolius Poiret (Rosaceae) was introduced to the island of Réunion in the southeastern Indian Ocean about 1850 and is now highly invasive. This bramble, native from southeastern Asia and Malaysia, has invaded a wide variety of habitats (lowland rainforest, mountain and submountain rainforest, Acacia heterophylla rainforest) from sea level to 1700 m. It is suspected to be monoclonal so, its remarkable success may be due in part to great phenotypic plasticity. On Réunion, bud, flower, fruit and seed production, the duration of the flowering period and the importance of the seed bank were found to be negatively correlated with elevation (50-1500 m a.s.l.). At a lowland site, fruit production in mature stands averaged between 30 and 80 fruits/m² during 1999 and 2000. No fruit set occurred above 1100 m. This fruit production pattern was similar over two years. Although the number of leaves per unit area is similar along the whole gradient studied, decrease of fruit set in upland areas might be compensated for by an increase in vegetative growth. Temperature variation is very sharp along the elevation gradient and may control the fruit and the seed production. Fruit production allows establishment of new populations all around the island via bird dissemination. Once established, R. alceifolius maintains dense patches that can grow vegetatively. Our results may be relevant for eradication programs that should take into account variation in reproductive strategy in lowland vs. highland habitats.     

Development of glial cells cultured from prenatally alcohol treated rat brain: Effect of supplementation of the maternal alcohol diet with a grape extract

The aim of this work was to investigate the effect of supplementation of a maternal alcohol diet with a grape extract on glial cell development. Glial cells were cultured during 4 weeks from cortical brain cells of the new born offspring in DMEM medium supplemented with fetal calf serum. Enzymatic markers of nerve cell development were measured (enolase isoenzymes and glutamine synthetase). Since alcohol consumption produces free radicals the antioxidant system superoxide dismutase was also investigated. Compared to the decrease found in only alcohol treated animals, all parameters except neuron-specific enolase were antagonized and even stimulated after grape extract supplementation. The effect was more important after only 1 month than 3 months of treatment. Also in the total brain an alcohol antagonizing effect and a glutamine synthetase activation were found. Our data demonstrate that addition of a grape extract to the maternal alcohol diet may partially or completely overcome the alcohol induced retardation of glial cell development.     

Elucidation of the mechanism involved in the regulation of protease production by immobilizedMyxococcus xanthus cells

Summary The mechanism involved in the positive effect of immobilization on protease production byMyxococcus xanthus was investigated. The results have shown that this phenomenon was not related to the difficulty encountered by the potential repressors to diffuse through the gel beads. The positive effect of immobilization on protease synthesis is the result of a different physiological state of the cells due to the stress caused by immobilization.     

Rapid method for detecting Desulfitobacterium frappieri strain PCP-1 in soil by the polymerase chain reaction

A rapid method was developed for detecting in soil Desulfitobacterium frappieri strain PCP-1, an anaerobic gram-positive bacterium, isolated from a methanogenic consortium degrading pentachlorophenol. The method involved the establishment of a protocol for extracting total DNA from soil with the least contamination, and the use of the polymerase chain reaction (PCR) to detect strain PCP-1 with primers targeted with PCP-1 16S rRNA. To optimize the DNA extraction conditions, a glass mill homogenizer and a low-salt buffer containing polyvinylpolypyrrolidone were used on a black soil rich in organic matter. Recovered DNA was further purified with phenol/chloroform extractions, ammonium acetate precipitation and a G200 Sephadex gel-filtration column. DNA was extracted from soil supplemented with different concentrations of PCP-1 cells. Detection of PCP-1 was by PCR. The limit of detection was 800 added PCP-1 cells/g dry soil. This level of detection was achieved when the T4 gene-32 protein and 1 μg soil DNA were added to the PCR mixture followed by a nested PCR. This method is quick, sensitive, and can process several samples at the same time. Received: 22 October 1996 / Received revision: 24 January 1997 / Accepted: 10 February 1997     

Distal Val346Ile mutation in inducible NO synthase promotes substrate-dependent NO confinement

The function of inducible NO synthase (WT iNOS) depends on the release of NO from the ferric heme before the enzyme is reduced. Key parameters controlling ligand dynamics include the distal and proximal heme pocket amino acids, as well as the inner solvent molecules. In this work, we tested how a point mutation in the distal heme side of WT iNOS affected the geminate rebinding of NO by ultrafast kinetics and molecular dynamics simulations. The mutation sequestered much of the photodissociated NO close to the heme compared to WT iNOS, with a main picosecond phase accounting for 78% of the rebinding to the arginine-bound Val346Ile protein. Consequently, the probability of NO release from Val346Ile decreased as compared to that from WT iNOS, provided the substrate binding site is filled. These data are rationalized by a steric effect of the Ile methyl group inducing events mediated by the substrate, transmitted via the propionates to the NO and the protein. This model is consistent with the role of the H-bonding network involving the heme, the substrate, and the BH4 cofactor in controlling NO release, with a key role of the heme propionates [Gautier et al. (2006) Nitric Oxide 15, 312]. These data support the effect of Val346Ile mutation in decreasing NO release and slowing down NO synthesis compared to WT iNOS determined by single turnover catalysis [Wang et al. (2004) J. Biol. Chem. 279, 19018].