Structural basis for apoptosis inhibition by Epstein-Barr virus BHRF1

Epstein-Barr virus (EBV) is associated with human malignancies, especially those affecting the B cell compartment such as Burkitt lymphoma. The virally encoded homolog of the mammalian pro-survival protein Bcl-2, BHRF1 contributes to viral infectivity and lymphomagenesis. In addition to the pro-apoptotic BH3-only protein Bim, its key target in lymphoid cells, BHRF1 also binds a selective sub-set of pro-apoptotic proteins (Bid, Puma, Bak) expressed by host cells. A consequence of BHRF1 expression is marked resistance to a range of cytotoxic agents and in particular, we show that its expression renders a mouse model of Burkitt lymphoma untreatable. As current small organic antagonists of Bcl-2 do not target BHRF1, the structures of it in complex with Bim or Bak shown here will be useful to guide efforts to target BHRF1 in EBV-associated malignancies, which are usually associated with poor clinical outcomes.     

The effects of tidal advection and mixing on the statistical dispersion of zooplankton

Series of six repeated vertical Zooplankton hauls 5 min apart were made on a hourly basis during 7 h at an anchor station in the upper St. Lawrence Estuary, Québec. A hierarchical analysis of variance showed that hour-to-hour variations in numbers of most Zooplankton components were of greater magnitude than those found within 30 min or caused by counting errors.The increase of variance for increasing lengths of the sampling period was investigated using a 175 h time series of Zooplankton samples taken 30 min apart at the same location. The results show that the confidence interval of a single observation at the anchor station increases as the scale of the experiment approaches that of the main advective processes (semidiurnal tidal currents) after which it remains relatively stable. For a given sampling scale, the statistical dispersion of Zooplankton is not permanent but varies in time and space under the effects of tidal advection and mixing. These results show that, in tidal estuaries, advection phenomena are more easily recognizable than turbulence effects.     

Nitrate reductase and cytochrome bnitrate reductase structural genes as parts of the nitrate reductase operon

Summary The existence of a nitrate-reductase operon in the tryptophane region was deduced from the effects of prophage insertion in each of chl I and chl C genes and from transposition of the Mu-mediated host DNA fragments on F-prime. This operon appears to be polarized from chlC to chlI and the gene order in the region is trp-chlI-chlC-purB.     

Nitrogen allocation in response to partial shading of a plant: Possible mechanisms

The significance of photosynthetic and transpiration rates for the perception by plants of light gradients in leaf canopies has been investigated with regard to nitrogen allocation and re-allocation. A gradient of photon flux density (PFD) over a plant's foliage was simulated by shading one leaf of a pair of primary leaves of bean ( Phaseolus vulgaris L. cv. Rentegever). Photosynthetic rate was manipulated independently of PFD and, to some extent, also of transpiration, by subjecting the leaf to different CO₂ concentrations. Transpiration rate was changed independently of PFD and photosynthetic rate by subjecting the leaf to different vapour pressure differences (VPD). A reduced partial pressure of CO₂ reduced specific leaf mass (SLM) as did a decreased PFD, but did not change leaf N per unit area (N_LA) and light saturated rate of photosynthesis (A_max). A reduced VPD caused several effects consistent with the effect of PFD. It decreased N_LA and A_max and increased the chlorophyll to N ratio in old and young leaves. Furthermore, it decreased the chlorophyll a to b ratio and inhibited leaf growth in young leaves. The transpiration stream is partitioned among the leaves of a plant according to their transpiration rates. The results suggest that relative rates of import of xylem sap into leaves of a plant play an important role in the perception of partial shading of a plant, a situation normally found in dense vegetations. The possible role of cytokinin influx into leaves as controlled by transpiration rate, is discussed.     

Juvenile animal studies for the development of paediatric medicines: a description and conclusions from a European medicines agency workshop on juvenile animal testing for nonclinical assessors

A workshop organised by the European Medicines Agency involved assessors and experts present in a Nonclinical Working Group evaluating juvenile animal studies for Paediatric Investigation Plans in collaboration with the Paediatric Committee and the Safety Working Party of the Committee for Human Medicinal Products. The objective of the workshop was to analyse which juvenile animal studies proposals were received and agreed by the Paediatric Committee, to check consistency and how to apply the existing European guideline on juvenile animal studies. A comparison of main organ system development in man vs. animal species was presented to guide the review and to support species selection and protocol design. An analysis of juvenile animal studies included in finalised PIP's was also presented. Out of 109 paediatric investigation plans finalised between November 2008 and March 2009, 43 included one or more juvenile animal studies. In most cases the preferred species was the rat; one species only was requested to be studied (20/22), but in a minority two species were required (2/22). When deciding on the characteristics of the juvenile animal studies, such as age of animals at study start, the age of the children targeted by the medicine was considered. It is expected that the increasing experience gained by Applicants and Regulators will allow further refining the criteria for these juvenile animal studies. Further research on this topic is highly encouraged in the European Regulatory framework. Birth Defects Res (Part B) 89:467–473, 2010. © 2010 Wiley‐Liss, Inc.     

Has Armstrong's cycle efficiency improved?

This case describes the physiological maturation from ages 21 to 28 yr of the bicyclist who has now become the six-time consecutive Grand Champion of the Tour de France, at ages 27-32 yr. Maximal oxygen uptake (Vo(2max)) in the trained state remained at approximately 6 l/min, lean body weight remained at approximately 70 kg, and maximal heart rate declined from 207 to 200 beats/min. Blood lactate threshold was typical of competitive cyclists in that it occurred at 76-85% Vo(2max), yet maximal blood lactate concentration was remarkably low in the trained state. It appears that an 8% improvement in muscular efficiency and thus power production when cycling at a given oxygen uptake (Vo(2)) is the characteristic that improved most as this athlete matured from ages 21 to 28 yr. It is noteworthy that at age 25 yr, this champion developed advanced cancer, requiring surgeries and chemotherapy. During the months leading up to each of his Tour de France victories, he reduced body weight and body fat by 4-7 kg (i.e., approximately 7%). Therefore, over the 7-yr period, an improvement in muscular efficiency and reduced body fat contributed equally to a remarkable 18% improvement in his steady-state power per kilogram body weight when cycling at a given Vo(2) (e.g., 5 l/min). It is hypothesized that the improved muscular efficiency probably reflects changes in muscle myosin type stimulated from years of training intensely for 3-6 h on most days.     

Cellular and molecular mechanisms involved in branching morphogenesis of the Drosophila tracheal system.

Recent comparative studies have shown that, in many instances, the genetic network underlying the development of distinct organ systems is similar in invertebrate and vertebrate organisms. Genetically well-characterized, simple invertebrate model systems, such as Caenorhabditis elegans and Drosophila melanogaster, can thus provide useful insight for understanding more complex organ systems in vertebrates. Here, we summarize recent progress in the genetic analysis of tracheal development in Drosophila and compare the results to studies aimed at a better understanding of lung development in mouse and man. Clearly, both striking similarities and important differences are apparent, but it might still be too early to conclude whether the former or the latter prevail.     

Endocrine regulation of energy metabolism by the skeleton

The regulation of bone remodeling by an adipocyte-derived hormone implies that bone may exert a feedback control of energy homeostasis. To test this hypothesis we looked for genes expressed in osteoblasts, encoding signaling molecules and affecting energy metabolism. We show here that mice lacking the protein tyrosine phosphatase OST-PTP are hypoglycemic and are protected from obesity and glucose intolerance because of an increase in beta-cell proliferation, insulin secretion, and insulin sensitivity. In contrast, mice lacking the osteoblast-secreted molecule osteocalcin display decreased beta-cell proliferation, glucose intolerance, and insulin resistance. Removing one Osteocalcin allele from OST-PTP-deficient mice corrects their metabolic phenotype. Ex vivo, osteocalcin can stimulate CyclinD1 and Insulin expression in beta-cells and Adiponectin, an insulin-sensitizing adipokine, in adipocytes; in vivo osteocalcin can improve glucose tolerance. By revealing that the skeleton exerts an endocrine regulation of sugar homeostasis this study expands the biological importance of this organ and our understanding of energy metabolism.     

Genetic Diversity of <Emphasis Type="Italic">Acacia seyal</Emphasis> Del. Rhizobial Populations Indigenous to Senegalese Soils in Relation to Salinity and pH of the Sampling Sites

The occurrence and the distribution of rhizobial populations naturally associated to Acacia seyal Del. were characterized in 42 soils from Senegal. The diversity of rhizobial genotypes, as characterized by polymerase chain reaction restriction fragment length polymorphism (RFLP) analysis of 16S–23S rDNA, performed on DNA extracted from 138 nodules resulted in 15 clusters. Results indicated the widespread occurrence of compatible rhizobia associated to A. seyal in various ecogeographic areas. However, the clustering of rhizobial populations based on intergenic spacer (IGS) RFLP profiles did not reflect their geographic origin. Four genera were discriminated on the basis of 16S rRNA gene sequences of the strains representative for the IGS-RFLP profiles. The majority of rhizobia associated to A. seyal were affiliated to Mesorhizobium and Sinorhizobium 64 and 29%, respectively, of the different IGS-RFLP profiles. Our results demonstrate the coexistence inside the nodule of plant-pathogenic non-N₂-fixing Agrobacterium and Burkholderia strains, which induced the formation of ineffective nodules, with symbiotic rhizobia. Nodulation was recorded in saline soils and/or at low pH values or in alkaline soils, suggesting adaptability of natural rhizobial populations to major ecological environmental stress and their ability to establish symbiotic associations within these soil environments. These results contribute to the progressing research efforts to uncover the biodiversity of rhizobia and to improve nitrogen fixation in agroforestry systems in sub-Saharan Africa.