Synthesis of an ochre suppressor tRNA gene and expression in mammalian cells.

Journal ArticleWe have used site-specific mutagenesis to change the anticodon of a Xenopus laevis tyrosine tRNA gene so that it would recognize ochre codons. This tRNA gene is expressed when amplified in monkey cells as part of a SV40 recombinant and efficiently suppresses termination at both the ochre codon separating the adenovirus 2 hexon gene from a 23-kd downstream gene and the ochre codon at the end of the NS1 gene of influenza virus A/Tex/1/68. Termination at an amber codon of a NS1 gene of another influenza virus strain was not suppressed by the (Su+) ochre gene suggesting that in mammalian cells amber codons are not recognized by ochre suppressor tRNAs. Finally, microinjection into mammalian cells of both (Su+) ochre tRNA genes and selectible genes containing ochre nonsense mutations gives rise to colonies under selective conditions. We conclude that it should be possible to isolate a wide assortment of mammalian cell lines with ochre suppressor activity

High Temperature Microplasticity of Fine-Grained Ceramics

Several fine-grained ceramics exhibit enhanced ductility or even structural superplasticity at high temperature. Grain boundaries play a dominant role in the deformation process of these materials which usually involves diffusion-accommodated grain boundary sliding. Sliding is either lubricated by an amorphous intergranular phase or takes place by glide and climb of grain boundary dislocations. At high temperature, anelastic deformation precedes plastic deformation and stems from the short range motion of lattice defects, such as dislocations and grain boundaries. The energy loss ("mechanical loss") associated with such motion can be measured by using the technique of mechanical spectroscopy. Moreover, at the onset of plasticity ("microplasticity"), long range irrecoverable motion of defects contributes to additional mechanical loss. Mechanical loss spectra may then give an insight into mechanisms operating at the transition between anelastic and plastic deformation. As an illustration, the spectra of three fine-grained ceramics (Si3N4, ZrO2, Al2O3) are presented. In all cases, anelastic relaxation phenomena (peak and background) have been observed at high temperature (>1200K), bearing a close relation with creep behaviour. Their analysis permits to distinguish between different types of microstructural elements : bulk regions of amorphous intergranular phase at triple points, grain boundaries separated by a thin glassy film and "clean" grain boundaries

An Examination of the Use of Trait Association Analysis and Genetic Variation to Identify Quantitative Traits in Indian Mustard (Brassica juncea L.)

The experiment was carried out throughout the winter season rabi under irrigated and rainfed conditions to examine the durability of enhanced and high-yielding cultivars of Indian mustard. Variance analysis on 14 characters was performed individually as well as aggregated across years and places. Irrigated environments were better for expressing a larger range of characters and a higher mean for all characters. Days to maturity, plant height, point to first branch, primary branches/plant, secondary branches/plant, point to first siliqua, seed yield/plant, and days to 50% flowering all showed significant G E interaction, indicating a significant amount of predictable G E interaction. All genotypes passed the tests for the three stability parameters and were found to be stable and high yielding. Although genotype were shown to be appropriate for growth in rainfed (poor) conditions despite having greater performance for seed yield/plant. The "genotype" was discovered to be suited for production in an irrigated (beneficial) environment and outperformed the population mean forseed yield/plant. Any breeding plan that aims to create stable, high-yielding genotypes can contain genotypes. For an increase in seed yield per plant, direct selection in the segregating generations of such parents for 1000-seed weight, point to first branch, secondary branches/plant, siliqua length, and overall number of siliquae/plant will be effective (PDF) Stability analysis in Indian mustard