Enzyme activities in aged conidia of N. crassa

Enzyme activities in aged conidia of N. crass

The receptors for gibbon ape leukemia virus and amphotropic murine leukemia virus are not downregulated in productively infected cells

<p>Abstract</p> <p>Background</p> <p>Over the last several decades it has been noted, using a variety of different methods, that cells infected by a specific gammaretrovirus are resistant to infection by other retroviruses that employ the same receptor; a phenomenon termed receptor interference. Receptor masking is thought to provide an earlier means of blocking superinfection, whereas receptor down regulation is generally considered to occur in chronically infected cells.</p> <p>Results</p> <p>We used replication-competent GFP-expressing viruses containing either an amphotropic murine leukemia virus (A-MLV) or the gibbon ape leukemia virus (GALV) envelope. We also constructed similar viruses containing fluorescence-labeled Gag proteins for the detection of viral particles. Using this repertoire of reagents together with a wide range of antibodies, we were able to determine the presence and availability of viral receptors, and detect viral envelope proteins and particles presence on the cell surface of chronically infected cells.</p> <p>Conclusions</p> <p>A-MLV or GALV receptors remain on the surface of chronically infected cells and are detectable by respective antibodies, indicating that these receptors are not downregulated in these infected cells as previously proposed. We were also able to detect viral envelope proteins on the infected cell surface and infected cells are unable to bind soluble A-MLV or GALV envelopes indicating that receptor binding sites are masked by endogenously expressed A-MLV or GALV viral envelope. However, receptor masking does not completely prevent A-MLV or GALV superinfection.</p

Shifts in Species Composition Constrain Restoration of Overgrazed Grassland Using Nitrogen Fertilization in Inner Mongolian Steppe, China

Long-term livestock over-grazing causes nitrogen outputs to exceed inputs in Inner Mongolia, suggesting that low levels of nitrogen fertilization could help restore grasslands degraded by overgrazing. However, the effectiveness of such an approach depends on the response of production and species composition to the interactive drivers of nitrogen and water availability. We conducted a five-year experiment manipulating precipitation (NP: natural precipitation and SWP: simulated wet year precipitation) and nitrogen (0, 25 and 50 kg N ha-1 yr-1) addition in Inner Mongolia. We hypothesized that nitrogen fertilization would increase forage production when water availability was relatively high. However, the extent to which nitrogen would co-limit production under average or below average rainfall in these grasslands was unknown

Effects-based Operations and the Problem of Causality; Simple and Complex

It has become fashionable in most armed forces worldwide to go “effectsbased.” The 2006 Quadrennial Defense Review Report emphasizes explicitly the need to make the shift “from massing forces—to massing effects” and “from focusing on inputs (effort) to tracking outputs(results).”1 In a similar fashion, the North Atlantic Treaty Organization (NATO)is adopting the effects-based approach in order to drive force employment and transformation. The Alliance claims that its interest in effects in military operations represents “a fundamental way of thinking that focuses on the efficient and effective achievement of desired effects in the operational environment, vice a primary focus on the completion of assigned tasks.”2 Armed forces outside NATO are moving in an effects-based direction, too; for example, the Israel Defense Force chief of staff emphasized that force transformation issues must focus less on forc and power but more on effect.3 It appears that nothing can stand against the power that comes from a causal focus aimed at achieving various sorts of effects on the enemy. However, there are many reasons to be doubtful regarding the practical utility of effects-based operations and the effects-based approach in general. Thus, the aim of this article is to address some basic assumptions upon which the two neologisms are built and analyze whether those assumptions are valid

Cloning and characterization of the genes of the CeqI restriction-modification system

Two genes from Corynebacterium equii, a Gram-positive bacterium producing the CeqI restriction—modification enzymes were cloned and sequenced. In vivo restriction experiments, DNA and amino acid sequence data suggest that the two genes code for the endonuclease and the methyltransferase enzymes. However, when the two genes are expressed in E. coli, practically no enzyme activity can be detected in the supernatants of sonicated cells. Based on the DNA sequence data CeqI restriction endonuclease (an EcoRV izoschizomer) consists of 270 amino acid residues with a predicted molecular mass of 31.6 kDa, in good agreement with the previously measured 32 ± 2 kDa. The methyltransferase is 517 residues long (approx. 60 kDa). The two genes are in opposite orientation and overlap by 37 base pairs on the chromosome. The deduced amino acid sequence of the putative endonuclease gene revealed long stretches of hydrophobic amino acids, that may form the structural basis of the unusual aggregation properties of the restriction endonuclease. The amino acid sequence of the methylase shows homologies with other type II methyltransferases

One-step unidirectional cloning of tandem repeats of DNA fragments: An application for fusion protein production

link_to_subscribed_fulltex