Stimulated ionization scattering of a wave beam forming a discharge channel in a magnetic mirror trap

The stimulated scattering of a whistler wave beam forming an extended discharge channel in a magnetic mirror trap is discovered and investigated experimentally. It is shown that the beam is scattered by relaxaction oscillations of the lattice of plasma inhomogeneities excited by the beam field. The spectrum of the pump field in the RF discharge plasma is found to broaden considerably and to contain individual modulation peaks corresponding to lattice oscillations. The peaks are observed at working gas pressures at which the electron mean free path is close to the wavelength of the standing wave forming the discharge channel. A physical model describing the phenomena observed is developed.     

Rubella in Russia: variability of the infectious agent during the period of vaccine prophylaxis

AIM: To assess influence of vaccination against rubella on the genetic diversity of rubella virus. MATERIALS AND METHODS: Vaccine strains of rubella virus Wistar 27/3 and Orlov-B as well as sera from patients with rubella obtained in Perm region during 1999 - 2005 period and standard serologic, molecular, epidemiologic and statistical methods were used. The study was performed according to the WHO recommendations on the genotyping of wild rubellavirus strains. RESULTS: Strains of rubella virus isolated in Perm region, vaccine strain Orlov-B (Saint Petersburg), and 4 Russian strains isolated in 1967-1997 before vaccine introduction belong to the same genetic group with high degree of homology - genetic divergence do not exceed 0 - 1%. This group was identified as genotype 2c which, according to WHO's data, circulates only in Russia. Periods of epidemic peaks of rubella incidence and its falls as well as selective immunization of girls and women of childbearing age did not influence on the genetic stability of the virus (divergence did not exceed 0.6 - 2.0%). On the contrary, mass immunization of children aged 1 - 2 years during 4 years resulted in statistically significant changes of rubella virus subtype inside the genotype 2c. CONCLUSION: Ten-year experience of rubella vaccination in Perm region demonstrates necessity of inclusion of monitoring for rubella virus variability in the system of epidemiological surveillance and control for rubella infection during period of its prevention by vaccine.     

Inheritance of fertility in broiler chickens

Background

The fertility of a chicken''s egg is a trait which depends on both the hen that lays the egg and on her mate. It is also known that fertility of an individual changes over the laying period.

Methods

Longitudinal models including both random genetic and permanent environmental effects of both the female and her male mate were used to model the proportion of fertile eggs in a pedigree broiler population over the ages 29-54 weeks.

Results

Both the male and the female contribute to variation in fertility. Estimates of heritability of weekly records were typically 7% for female and 10% for male contributions to fertility. Repeatability estimates ranged from 24 to 33%, respectively. The estimated genetic variance remained almost constant for both sexes over the laying period and the genetic correlations between different ages were close to 1.0. The permanent environment components increased substantially towards the end of the analyzed period, and correlations between permanent environment effects at different ages declined with increasing age difference The heritability of mean fertility over the whole laying period was estimated at 13% for females and 17% for males. A small positive correlation between genetic effects for male and female fertility was found.

Conclusion

Opportunities to improve fertility in broiler stocks by selection on both sexes exist and should have an impact throughout the laying period.     

Genetic heterogeneity of residual variance in broiler chickens

Aims were to estimate the extent of genetic heterogeneity in environmental variance. Data comprised 99 535 records of 35-day body weights from broiler chickens reared in a controlled environment. Residual variance within dam families was estimated using ASREML, after fitting fixed effects such as genetic groups and hatches, for each of 377 genetically contemporary sires with a large number of progeny (> 100 males or females each). Residual variance was computed separately for male and female offspring, and after correction for sampling, strong evidence for heterogeneity was found, the standard deviation between sires in within variance amounting to 15–18% of its mean. Reanalysis using log-transformed data gave similar results, and elimination of 2–3% of outlier data reduced the heterogeneity but it was still over 10%. The correlation between estimates for males and females was low, however. The correlation between sire effects on progeny mean and residual variance for body weight was small and negative (-0.1). Using a data set bigger than any yet presented and on a trait measurable in both sexes, this study has shown evidence for heterogeneity in the residual variance, which could not be explained by segregation of major genes unless very few determined the trait.     

Window on a Microworld: Simple Microfluidic Systems for Studying Microbial Transport in Porous Media

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in the environment, as well as directly for the transmission of pathogens to drinking water supplies. Natural porous media is composed of an intricate physical topology, varied surface chemistries, dynamic gradients of nutrients and electron acceptors, and a patchy distribution of microbes. These features vary substantially over a length scale of microns, making the results of macro-scale investigations of microbial transport difficult to interpret, and the validation of mechanistic models challenging. Here we demonstrate how simple microfluidic devices can be used to visualize microbial interactions with micro-structured habitats, to identify key processes influencing the observed phenomena, and to systematically validate predictive models. Simple, easy-to-use flow cells were constructed out of the transparent, biocompatible and oxygen-permeable material poly(dimethyl siloxane). Standard methods of photolithography were used to make micro-structured masters, and replica molding was used to cast micro-structured flow cells from the masters. The physical design of the flow cell chamber is adaptable to the experimental requirements: microchannels can vary from simple linear connections to complex topologies with feature sizes as small as 2 μm. Our modular EcoChip flow cell array features dozens of identical chambers and flow control by a gravity-driven flow module. We demonstrate that through use of EcoChip devices, physical structures and pressure heads can be held constant or varied systematically while the influence of surface chemistry, fluid properties, or the characteristics of the microbial population is investigated. Through transport experiments using a non-pathogenic, green fluorescent protein-expressing Vibrio bacterial strain, we illustrate the importance of habitat structure, flow conditions, and inoculums size on fundamental transport phenomena, and with real-time particle-scale observations, demonstrate that microfluidics offer a compelling view of a hidden world.Download video file.^{(163M, mp4)}     

Association of genes of different functional classes with type 1 diabetes

The genetic structure of susceptibility to type 1 diabetes (T1D) in the population of Tomsk was studied. We had a group of T1D patients (N = 285) and a population sample (N = 300) and we studied 58 SNPs localized in the 47 genes which products are involved in various metabolic pathways and processes as fibrogenesis, endothelial dysfunction, and inflammation. Genotyping was performed by mass spectrometry using the Sequenom MassARRAY system (United States). We compared the group of T1D patients and the population sample and found an association with the predisposition to disease for seven markers: rs3765124 of the ADAMDEC1 gene, genotype AA (p = 0.004), allele A (p = 0.033); rs1007856 of the ITGB5 gene, genotype TT (p = 0.015), allele T (p = 0.036); rs20579 of the LIG1 gene, genotype CC (p = 0.004), allele C (p = 0.002); rs12980602 of the IFNL2 gene, allele C (p = 0.029); rs4986819 of the PARP4 gene, allele C (p = 0.044); rs1143674 of the ITGA4 gene genotype GG (p = 0.002); rs679620 of the MMP3 gene, genotype AA (p = 0.008). Thus, the products of genes associated with T1D belong to different molecular classes: metalloproteases (ADAMDEC1, MMP3), cytokines (IL28A), cell surface receptors (ITGA4), adhesion molecules (ITGB5), DNA ligases (LIG1), and ribosyltransferase enzymes (PARP4). The ADAMDEC1, ITGA4, and ITGB5 genes belong to two biological processes: cell communication and signal transduction. The LIG1 and PARP4 genes regulate the metabolism of nucleic acids, MMP3 is involved in the regulation of protein metabolism, and the IFNL2 is involved in the immune response.     

Adaptive phylogeography: functional divergence between haemoglobins derived from different glacial refugia in the bank vole

Over the years, researchers have used presumptively neutral molecular variation to infer the origins of current species'' distributions in northern latitudes (especially Europe). However, several reported examples of genic and chromosomal replacements suggest that end-glacial colonizations of particular northern areas may have involved genetic input from different source populations at different times, coupled with competition and selection. We investigate the functional consequences of differences between two bank vole (Clethrionomys glareolus) haemoglobins deriving from different glacial refugia, one of which partially replaced the other in Britain during end-glacial climate warming. This allows us to examine their adaptive divergence and hence a possible role of selection in the replacement. We determine the amino acid substitution Ser52Cys in the major expressed β-globin gene as the allelic difference. We use structural modelling to reveal that the protein environment renders the 52Cys thiol a highly reactive functional group and we show its reactivity in vitro. We demonstrate that possessing the reactive thiol in haemoglobin increases the resistance of bank vole erythrocytes to oxidative stress. Our study thus provides striking evidence for physiological differences between products of genic variants that spread at the expense of one another during colonization of an area from different glacial refugia.