The AtRbx1 protein is part of plant SCF complexes,and its down-regulation causes severe growth and developmental defects

Recently in yeast and animal cells, one particular class of ubiquitin ligase (E3), called the SCF, was demonstrated to regulate diverse processes including cell cycle and development. In plants SCF-dependent proteolysis is also involved in different developmental and hormonal regulations. To further investigate the function of SCF, we characterized at the molecular level the Arabidopsis RING-H2 finger protein AtRbx1. We demonstrated that the plant gene is able to functionally complement a yeast knockout mutant strain and showed that AtRbx1 protein interacts physically with at least two members of the Arabidopsis cullin family (AtCul1 and AtCul4). AtRbx1 also associates with AtCul1 and the Arabidopsis SKP1-related proteins in planta, indicating that it is part of plant SCF complexes. AtRbx1 mRNAs accumulate in various tissues of the plant, but at higher levels in tissues containing actively dividing cells. Finally to study the function of the gene in planta, we either overexpressed AtRbx1 or reduced its expression by a dsRNA strategy. Down-regulation of AtRbx1 impaired seedling growth and development, indicating that the gene is essential in plants. Furthermore, the AtRbx1-silenced plants showed a reduced level of AtCul1 protein, but accumulated higher level of cyclin D3.     

Fatal outcome of sleep apnoea in PWS during the initial phase of growth hormone treatment. A case report

The case of a boy with Prader-Willi syndrome (PWS) who suffered from respiratory problems since birth and suddenly died at the age of 6.5 years, 4 months after initiation of GH therapy, is presented. This case indicates the possibility of fatal courses in infants and children with PWS as a consequence of respiratory problems and raises the question as to a causal connection between the initiation of GH therapy and the sudden death of this child.     

Seasonal variation in leaf chemistry of the coast live oak Quercus agrifolia and implications for the California oak moth Phryganidia californica

Summary The perennial foliage of the California coast live oak (Quercus agrifolia Nee) permits herbivores to feed on this oak species throughout the year. Patterns of herbivory for a two-year period on Q. agrifolia were observed in relation to seasonal and age-related changes in the nutritional and defensive characteristics of leaves. Nitrogen and phosphorus contents were higher in new leaves compared to mature foliage. Structural compounds (e.g., cellulose) in leaves rapidly increased with age. Concentrations of tatal phenolics (Folin-Denis) and astringency were higher in new foliage, and concentrations of condensed tannins gradually increased as the leaves matured. Peaks of herbivore damage were observed in June and in September–October, and were caused by outbreaks of the California oak moth (Phryganidia californica). P. californica, a bivoltine oak specialist, exhibited feeding preferences in June for old leaves over emerging leaves, and showed no preferences for leaf classes in September. These results suggest that P. californica is adapted to survive on nutritionally poor foliage and to circumvent quantitative defenses such as condensed tannins.     

Kinetics of IL-7 and IL-15 Levels after Allogeneic Peripheral Blood Stem Cell Transplantation following Nonmyeloablative Conditioning

Background

We analysed kinetics of IL-7 and IL-15 levels in 70 patients given peripheral blood stem cells after nonmyeloablative conditioning.

Methods

EDTA-anticoagulated plasma and serum samples were obtained before conditioning and about once per week after transplantation until day 100. Samples were aliquoted and stored at −80°C within 3 hours after collection until measurement of cytokines. IL-7 and IL-15 levels were measured by ELISAs.

Results

Median IL-7 plasma levels remained below 6 pg/L throughout the first 100 days, although IL-7 plasma levels were significantly higher on days 7 (5.1 pg/mL, P = 0.002), 14 (5.2 pg/mL, P<0.001), and 28 (5.1 pg/mL, P = 0.03) (but not thereafter) than before transplantation (median value of 3.8 pg/mL). Median IL-15 serum levels were significantly higher on days 7 (12.5 pg/mL, P<0.001), 14 (10.5 pg/mL, P<0.001), and 28 (6.2 pg/mL, P<0.001) than before transplantation (median value of 2.4 pg/mL). Importantly, IL-7 and IL-15 levels on days 7 or 14 after transplantation did not predict grade II–IV acute GVHD.

Conclusions

These data suggest that IL-7 and IL-15 levels remain relatively low after nonmyeloablative transplantation, and that IL-7 and IL-15 levels early after nonmyeloablative transplantation do not predict for acute GVHD.     

Characterization of the cell death induced by cadmium in HaCaT and C6 cell lines

Cell death resulting from cadmium (Cd) intoxication has been confirmed to induce both necrosis and apoptosis. The ratio between both types of cell death is dose- and cell-type-dependent. This study used the human keratinocytes HaCaT expressing a mutated p53 and the rat glial cells C6 expressing a wild p53 as models to characterize Cd-induced apoptosis, using sub-lethal and lethal doses. At these concentrations, features of apoptosis were observed 24 h after C6 cell treatment: apoptotic DNA fragmentation and caspase-9 activation, whereas Cd did not induce caspase-3. In HaCaT, Cd did not induce apoptotic DNA fragmentation or caspase-9 and -3 activation. The results also showed that the inhibition of p53 led to a resistance of the C6 cells to 20 µm Cd, decreased the apoptosis and increased the metallothioneins in these cells. p53 restoration increased the sensitivity of HaCaT cells to Cd but did not affect the MT expression. The results suggest that Cd induced apoptosis in C6 cells but a non-apoptotic cellular death in HaCaT cells.     

A cellulase/xylanase-negative mutant of Streptomyces lividans 1326 defective in cellobiose and xylobiose uptake is mutated in a gene encoding a protein homologous to ATP-binding proteins

Centre de Recherche en Microbiologie Appliquée, Institut Armand-Frappier, Université du Québec, Ville de Laval, Québec H7N 4Z3, Canada.     

The relative importance of biological and chemical processes in the release of phosphorus from a highly organic sediment

Bacteria can play an important role in the process of anaerobic phosphorus release: they can act as a direct source of orthophosphates, or as a catalyst of iron hydroxyde reduction. We studied their influence on phosphorus release from highly organic sediments of a Canadian shield lake. Phosphorus and iron release were measured under aerobic and anaerobic conditions, with or without sterilization, and at different pH. We measured also the abundance and activity of bacteria in sediments. The increased P release after sterilization can be explained by cell lysis. Compared to sterilization, changing oxygen concentrations or acidification had little or no effect on P release. In these sediments, phosphorus and iron movements were independent. Most of the total dissolved iron seemed to be linked to humic acids, but not phosphorus.A contribution to the GRIL (Groupe de Recherche Interuniversitaire de Limnologie)     

Plasticity of Migrating CD1b+ and CD1b- Lymph Dendritic Cells in the Promotion of Th1, Th2 and Th17 in Response to Salmonella and Helminth Secretions

Dendritic cells (DCs) are pivotal in the development of specific T-cell responses to control pathogens, as they govern both the initiation and the polarization of adaptive immunity. To investigate the capacities of migrating DCs to respond to pathogens, we used physiologically generated lymph DCs (L-DCs). The flexible polarization of L-DCs was analysed in response to Salmonella or helminth secretions known to induce different T cell responses. Mature conventional CD1b⁺ L-DCs showed a predisposition to promote pro-inflammatory (IL-6), pro-Th1 (IL-12p40) and anti-inflammatory (IL-10) responses which were amplified by Salmonella, and limited to only IL-6 induction by helminth secretions. The other major population of L-DCs did not express the CD1b molecule and displayed phenotypic features of immaturity compared to CD1b⁺ L-DCs. Salmonella infection reduced the constitutive expression of TNF-α and IL-4 mRNA in CD1b^- L-DCs, whereas this expression was not affected by helminth secretions. The cytokine response of T cells promoted by L-DCs was analysed in T cell subsets after co-culture with Salmonella or helminth secretion-driven CD1b⁺ or CD1b^- L-DCs. T cells preferentially expressed the IL-17 gene, and to a lesser extent the IFN-γ and IL-10 genes, in response to Salmonella-driven CD1b⁺ L-DCs, whereas a preferential IL-10, IFN-γ and IL-17 gene expression was observed in response to Salmonella-driven CD1b^- L-DCs. In contrast, a predominant IL-4 and IL-13 gene expression by CD4⁺ and CD8⁺ T cells was observed after stimulation of CD1b⁺ and CD1b^- L-DCs with helminth secretions. These results show that mature conventional CD1b⁺ L-DCs maintain a flexible capacity to respond differently to pathogens, that the predisposition of CD1b^- L-DCs to promote a Th2 response can be oriented towards other Th responses, and finally that the modulation of migrating L-DCs responses is controlled more by the pathogen encountered than the L-DC subsets.