Mathematical Models of Incompressible Fluids as Singular Limits of Complete Fluid Systems

A rigorous justification of several well-known mathematical models of incompressible fluid flows can be given in terms of singular limits of the scaled Navier-Stokes-Fourier system, where some of the characteristic numbers become small or large enough. We discuss the problem in the framework of global-in-time solutions for both the primitive and the target system. © 2010 Springer Basel AG

Bacterial RuBisCO Is Required for Efficient Bradyrhizobium/Aeschynomene Symbiosis

Rhizobia and legume plants establish symbiotic associations resulting in the formation of organs specialized in nitrogen fixation. In such organs, termed nodules, bacteria differentiate into bacteroids which convert atmospheric nitrogen and supply the plant with organic nitrogen. As a counterpart, bacteroids receive carbon substrates from the plant. This rather simple model of metabolite exchange underlies symbiosis but does not describe the complexity of bacteroids' central metabolism. A previous study using the tropical symbiotic model Aeschynomene indica/photosynthetic Bradyrhizobium sp. ORS278 suggested a role of the bacterial Calvin cycle during the symbiotic process. Herein we investigated the role of two RuBisCO gene clusters of Bradyrhizobium sp. ORS278 during symbiosis. Using gene reporter fusion strains, we showed that cbbL1 but not the paralogous cbbL2 is expressed during symbiosis. Congruently, CbbL1 was detected in bacteroids by proteome analysis. The importance of CbbL1 for symbiotic nitrogen fixation was proven by a reverse genetic approach. Interestingly, despite its symbiotic nitrogen fixation defect, the cbbL1 mutant was not affected in nitrogen fixation activity under free living state. This study demonstrates a critical role for bacterial RuBisCO during a rhizobia/legume symbiotic interaction

CTCF Prevents the Epigenetic Drift of EBV Latency Promoter Qp

The establishment and maintenance of Epstein-Barr Virus (EBV) latent infection requires distinct viral gene expression programs. These gene expression programs, termed latency types, are determined largely by promoter selection, and controlled through the interplay between cell-type specific transcription factors, chromatin structure, and epigenetic modifications. We used a genome-wide chromatin-immunoprecipitation (ChIP) assay to identify epigenetic modifications that correlate with different latency types. We found that the chromatin insulator protein CTCF binds at several key regulatory nodes in the EBV genome and may compartmentalize epigenetic modifications across the viral genome. Highly enriched CTCF binding sites were identified at the promoter regions upstream of Cp, Wp, EBERs, and Qp. Since Qp is essential for long-term maintenance of viral genomes in type I latency and epithelial cell infections, we focused on the role of CTCF in regulating Qp. Purified CTCF bound ∼40 bp upstream of the EBNA1 binding sites located at +10 bp relative to the transcriptional initiation site at Qp. Mutagenesis of the CTCF binding site in EBV bacmids resulted in a decrease in the recovery of stable hygromycin-resistant episomes in 293 cells. EBV lacking the Qp CTCF site showed a decrease in Qp transcription initiation and a corresponding increase in Cp and Fp promoter utilization at 8 weeks post-transfection. However, by 16 weeks post-transfection, bacmids lacking CTCF sites had no detectable Qp transcription and showed high levels of histone H3 K9 methylation and CpG DNA methylation at the Qp initiation site. These findings provide direct genetic evidence that CTCF functions as a chromatin insulator that prevents the promiscuous transcription of surrounding genes and blocks the epigenetic silencing of an essential promoter, Qp, during EBV latent infection

Dichlorobis(cycloalkylamine)platinum(II) complexes. Structure activity relationship on the human MDA-MB-231 breast cancer cell line

The syntheses of dichlorobis(cycloalkylamine)platinum(II) complexes with cis and trans cycloalkylamine ligands [cis-PtCl2(C3H5NH2)2 to cis-PtCl2(C8H15NH2)2 and trans-PtCl2(C7H13NH2)2 and trans-PtCl2(C8H15NH2)2 are described. The distinction between cis and trans isomers was achieved by 1H-NMR spectroscopy. The antitumor activity was detd. on the cell proliferation of the human MDA-MB-231 breast cancer cell line during long-term drug exposure. The complexes with small cycloalkylamine ligands were inferior, those with large cycloalkylamine ligands were comparable or superior to cisplatin. All cycloalkylamine ligands were inactive. IR spectroscopic studies showed that the size of the cycloalkylamine ring does not lead to significant differences in the Pt-Cl binding strength. Therefore it is assumed that the markedly stronger antitumor activity of the higher homologs is not the result of a faster reaction with bionucleophiles such as DNA. A possible explanation of the high activity of some of the isomers is the strong lipophilicity of the complexes. This assumption was confirmed by toxicity tests against confluent cultures

Transferring Atlantic maritime pine improved material to a region with marked Mediterranean influence in inland NW Spain. A likelihood-based approach on spatially adjusted field data

The inland region of Galicia (NW Spain) marks the boundary between the Atlantic climate of the coastal area and the typical Mediterranean climate of central Spain. Compared to the Atlantic coast, climate in this area has a pronounced summer drought, lower annual precipitation, and higher annual thermal oscillation. Despite the high productivity and ecological importance of maritime pine in inland Galicia, local forest reproductive material (FRM) of high genetic quality is not available for this area. Seed sources originating elsewhere and of unknown adaptation to this area are commonly used for reforestation. With the aim of finding new sources of FRM for this region and exploiting the genetic gains of existing breeding programmes, we analysed the performance in field conditions of improved families of the Coastal Galicia (CG) and Western Australia (WA) breeding programmes. Growth, stem characteristics and branch habit were evaluated in five progeny trials established following a coastal-to-inland gradient. Likelihood-based analyses were used to estimate genetic correlations between environments and to test statistically for causes and patterns of genotype x environment interaction. Because of the strong non-random spatial structures and heterogeneity of residual variances, the analyses were carried out using heterogeneous residual variance mixed models on spatially adjusted data. The results indicated that there is not sufficient evidence to subdivide Galicia into the two current deployment areas. Interaction patterns do not reveal significant differences between zones, and crossover interactions for height growth are present both between and within areas. On the inland sites, the Atlantic improved materials clearly outperformed unimproved seedlots tested in adjacent provenance trials, suggesting the feasibility of using both the CG and WA breeding materials as sources of FRM for reforestation in inland Galicia. Of the two, the WA material showed excellent results for all traits. The inclusion of this material into the Galician maritime pine breeding population should be strongly considered.This study was supported by the Instituto Nacional de Tecnologia Agraria y Alimentaria (INIA) projects RTA05-173 and RTA07-100.Peer reviewe