EVA regulates thymic stromal organisation and early thymocyte development

Epithelial V-like antigen (EVA) is an immunoglobulin-like adhesion molecule identified in a screen for molecules developmentally regulated at the DN to DP progression in thymocyte development. We show that EVA is expressed during the early stages of thymus organogenesis in both fetal thymic epithelia and T cell precursors, and is progressively downregulated from day 16.5 of embryonic development. In the postnatal thymus, EVA expression is restricted to epithelial cells and is distributed throughout both cortical and medullary thymic regions. Transgenic overexpression of EVA in the thymus cortex resulted in a modified stromal environment, which elicited an increase in organ size and absolute cell number. Although peripheral T lymphocyte numbers are augmented throughout life, no imbalance either in the repertoire, or in the different T cell subsets was detected. Collectively, these data suggest a role for EVA in structural organisation of the thymus and early lymphocyte development.     

Regulation of tumor phenotypes by caveolin-1 and sphingolipid-controlled membrane signaling complexes

Aberrant (glyco)sphingolipid expression deeply affects several properties of tumor cells that are involved in tumor progression and metastasis formation: cell adhesion (to the extracellular matrix or to the endothelium of blood vessels), motility, recognition and invasion of host tissues. In particular, (glyco)sphingolipids might contribute to the modulation of integrin-dependent interactions of tumor cells (determining their adhesion, motility and invasiveness) with the extracellular matrix as well as with host cells present in the stromal compartment of the tumor. A model based on solid experimental evidence has been proposed: (glyco)sphingolipids at the cell surface interact with plasma membrane receptors (e.g., integrin receptors and growth factor receptors) and adapter molecules (including tetraspanins) forming signaling complexes that are able to influence the activity of signal transduction molecules oriented at the cytosolic surface of the plasma membrane (mainly the Src kinases pathway members). The function of these signaling complexes appears to be strictly dependent on their (glyco)sphingolipid composition, and likely on specific sphingolipid-protein interactions. From this point of view, particularly intriguing is the connection between (glyco)sphingolipids and caveolin-1, a membrane protein that plays multiple roles as a suppressor of tumor growth and metastasis in ovarian, breast and colon human carcinomas.     

Sexual differentiation of the rodent hypothalamus: hormonal and environmental influences

Brain sexual differentiation is a complex developmental phenomenon influenced by the genetic background, sex hormone secretions and environmental inputs, including pollution. The main hormonal drive to masculinize and defeminize the rodent brain is testosterone secreted by the testis. The hormone does not influence sex brain differentiation only in its native configuration, but it mostly needs local conversion into active metabolites (estradiol and DHT) through the action of specific enzymatic systems: the aromatase and 5alpha-reductase (5alpha-R), respectively. This allows the hormone to control target cell gene expression either through the estrogen (ER) or the androgen (AR) receptors. The developmental profile of testosterone metabolizing enzymes, different in the two sexes, is therefore of the utmost importance in affecting the bioavailability of the steroids active in brain differentiation. Widely diffused pollutants, like polychlorinated biphenyls (PCBs) are able to affect the production and/or action of testosterone metabolites, exerting detrimental influences on reproduction and sex behavior. The main studies performed in our and other laboratories concerning the pattern of expression and the control of the enzymatic systems involved in brain androgen action and metabolism are shortly reviewed. Some recent data on the influence exerted by PCBs on these metabolic systems are also reported.     

Non-invasive monitoring of the light-induced cyclic photosynthetic electron flow during cold hardening in wheat leaves

The effect of irradiance during low temperature hardening was studied in a winter wheat variety. Ten-day-old winter wheat plants were cold-hardened at 5 degrees C for 11 days under light (250 micromol m(-2) S(-1)) or dark (20 micromol m(-2) s(-1)) conditions. The effectiveness of hardening was significantly lower in the dark, in spite of a slight decrease in the Fv/Fm chlorophyll fluorescence induction parameter, indicating the occurrence of photoinhibition during the hardening period in the light. Hardening in the light caused a downshift in the far-red induced AG (afterglow) thermoluminescence band. The faster dark re-reduction of P700+, monitored by 820-nm absorbance, could also be observed in these plants. These results suggest that the induction of cyclic photosynthetic electron flow may also contribute to the advantage of frost hardening under light conditions in wheat plants.     

Impact of Age and Gender on the Prevalence and Prognostic Importance of the Metabolic Syndrome and Its Components in Europeans. The MORGAM Prospective Cohort Project

Objective

To investigate the influence of age and gender on the prevalence and cardiovascular disease (CVD) risk in Europeans presenting with the Metabolic Syndrome (MetS).

Methods

Using 36 cohorts from the MORGAM-Project with baseline between 1982–1997, 69094 men and women aged 19–78 years, without known CVD, were included. During 12.2 years of follow-up, 3.7%/2.1% of men/women died due to CVD. The corresponding percentages for fatal and nonfatal coronary heart disease (CHD) and stroke were 8.3/3.8 and 3.1/2.5.

Results

The prevalence of MetS, according to modified definitions of the International Diabetes Federation (IDF) and the revised National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII), increased across age groups for both genders (P<0.0001); with a 5-fold increase in women from ages 19–39 years to 60–78 years (7.4%/7.6% to 35.4%/37.6% for IDF/NCEP-ATPIII) and a 2-fold increase in men (5.3%/10.5% to 11.5%/21.8%). Using multivariate-adjusted Cox regressions, the associations between MetS and all three CVD events were significant (P<0.0001). For IDF/NCEP-ATPIII in men and women, hazard ratio (HR) for CHD was 1.60/1.62 and 1.93/2.03, for CVD mortality 1.73/1.65 and 1.77/2.06, and for stroke 1.51/1.53 and 1.58/1.77. Whereas in men the HRs for CVD events were independent of age (MetS*age, P>0.05), in women the HRs for CHD declined with age (HRs 3.23/3.98 to 1.55/1.56; MetS*age, P = 0.01/P = 0.001 for IDF/NCEP-ATPIII) while the HRs for stroke tended to increase (HRs 1.31/1.25 to 1.55/1.83; MetS*age, P>0.05).

Conclusion

In Europeans, both age and gender influenced the prevalence of MetS and its prognostic significance. The present results emphasise the importance of being critical of MetS in its current form as a marker of CVD especially in women, and advocate for a redefinition of MetS taking into account age especially in women.     

UV‐B radiation delays flowering time through changes in the PRC2 complex activity and miR156 levels in Arabidopsis thaliana

UV‐B is a high‐energy component of the solar radiation perceived by the plant and induces a number of modifications in plant growth and development, including changes in flowering time. However, the molecular mechanisms underlying these changes are largely unknown. In the present work, we demonstrate that Arabidopsis plants grown under white light supplemented with UV‐B show a delay in flowering time, and this developmental reprogramming is mediated by the UVR8 photoreceptor. Using a combination of gene expression analyses and UV‐B irradiation of different flowering mutants, we gained insight into the pathways involved in the observed flowering time delay in UV‐B‐exposed Arabidopsis plants. We provide evidence that UV‐B light downregulates the expression of MSI1 and CLF, two of the components of the polycomb repressive complex 2, which in consequence drives a decrease in H3K27me3 histone methylation of MIR156 and FLC genes. Modification in the expression of several flowering time genes as a consequence of the decrease in the polycomb repressive complex 2 activity was also determined. UV‐B exposure of flowering mutants supports the involvement of this complex in the observed delay in flowering time, mostly through the age pathway.     

Fluxes of N2O and CH4 from soils of savannas and seasonally-dry ecosystems

Aim Savannas and seasonally‐dry ecosystems cover a significant part of the world's land surface. If undisturbed, these ecosystems might be expected to show a net uptake of methane (CH₄) and a limited emission of nitrous oxide (N₂O). Land management has the potential to change dramatically the characteristics and gas exchange of ecosystems. The present work investigates the contribution of warm climate seasonally‐dry ecosystems to the atmospheric concentration of nitrous oxide and methane, and analyses the impact of land‐use change on N₂O and CH₄ fluxes from the ecosystems in question. Location Flux data reviewed here were collected from the literature; they come from savannas and seasonally‐dry ecosystems in warm climatic regions, including South America, India, Australasia and Mediterranean areas. Methods Data on gas fluxes were collected from the literature. Two factors were considered as determinants of the variation in gas fluxes: land management and season. Land management was grouped into: (1) control, (2) ‘burned only’ and (3) managed ecosystems. The season was categorized as dry or wet. In order to avoid the possibility that the influence of soil properties on gas fluxes might confound any differences caused by land management, sites were grouped in homogeneous clusters on the basis of soil properties, using multivariate analyses. Inter‐ and intra‐cluster analysis of gas fluxes were performed, taking into account the effects of season, land management and main vegetation types. Results Soils were often acid and nutrient‐poor, with low water retention. N₂O emissions were generally very low (median flux 0.32 mg N₂O m^?2 day^?1), and no significant differences were observed between woodland savannas and managed savannas. The highest fluxes (up to 12.9 mg N₂O m^?2 day^?1) were those on relatively fertile soils with high air‐filled porosity and water retention. The effect of season on N₂O production was evident only when sites were separated in homogeneous groups on the basis of soil properties. CH₄ fluxes varied over a wide range (?22.9 to 3.15 mg CH₄ m^?2 day^?1, where the negative sign denotes removal of gas from the atmosphere), with an annual average daily flux of ?0.48 ± 0.96 (SD) mg CH₄ m^?2 day^?1 in undisturbed (control) sites. Land‐use change dramatically reduced this CH₄ sink. Managed sites were weak sinks of CH₄ in the dry season and became sources of CH₄ in the wet season. This was particularly evident for pastures. Burning alone did not reduce soil net CH₄ oxidation, but decreased N₂O production. Main conclusions Despite the low potential for N₂O production, both in natural and managed conditions, tropical seasonally‐dry ecosystems represent a significant source of N₂O (4.4 Tg N₂O year^?1) on a global scale, as a consequence of the large area they occupy. The same environments represent a potential CH₄ sink of 5.17 Tg CH₄ year^?1. However, assuming that c. 30% of the tropical land is converted to different uses, the sink would be reduced to 3.2 Tg CH₄ year^?1. The limited information on fluxes from Mediterranean ecosystems does not allow a meaningful scaling up.     

Evidence of calcium- and SNARE-dependent release of CuZn superoxide dismutase from rat pituitary GH3 cells and synaptosomes in response to depolarization

The antioxidant enzyme CuZn superoxide dismutase (SOD1) is secreted by many cell lines. However, it is not clear whether SOD1 secretion is only constitutive or can be regulated in an activity-dependent fashion. Using rat pituitary GH(3) cells that express voltage-dependent calcium channels and are subjected to Ca(2+) oscillations, we found that treatment with high K(+)-induced SOD1 release that was significantly higher than the constitutive secretion. Evoked SOD1 release was correlated with depolarization-dependent calcium influx and was virtually abolished by removal of extracellular calcium with EGTA or by pre-incubation of GH(3) cells with Botulinum toxin A that cleaves the SNARE protein SNAP-25. Immunofluorescence experiments performed in GH(3) cells and rat brain synaptosomes showed that K(+)-depolarization induced a marked depletion of intracellular SOD1 immunoreactivity, an effect that was again abolished in the absence of extracellular calcium or after treatment with Botulinum toxin A. Subcellular fractionation analysis showed that SOD1 was present in large dense core vesicles. These data clearly show that, in addition to the constitutive SOD1 secretion, depolarization induces an additional rapid calcium-dependent SOD1 release in GH(3) cells and in rat brain synaptosomes. This likely occurs through exocytosis from SOD1-containing vesicles operated by the SNARE complex.     

Phosphotransfer reactions of the CbbRRS three-protein two- component system from Rhodopseudomonas palustris CGA010 appear to be controlled by an internal molecular switch on the sensor kinase

The CbbRRS system is an atypical three-protein two-component system that modulates the expression of the cbb(I) CO(2) fixation operon of Rhodopseudomonas palustris, possibly in response to a redox signal. It consists of a membrane-bound hybrid sensor kinase, CbbSR, with a transmitter and receiver domain, and two response regulator proteins, CbbRR1 and CbbRR2. No detectable helix-turn-helix DNA binding domain is associated with either response regulator, but an HPt domain and a second receiver domain are predicted at the C-terminal region of CbbRR1 and CbbRR2, respectively. The abundance of conserved residues predicted to participate in a His-Asp phosphorelay raised the question of their de facto involvement. In this study, the role of the multiple receiver domains was elucidated in vitro by generating site-directed mutants of the putative conserved residues. Distinct phosphorylation patterns were obtained with two truncated versions of the hybrid sensor kinase, CbbSR(T189) and CbbSR(R96) (CbbSR beginning at residues T189 and R96, respectively). These constructs also exhibited substantially different affinities for ATP and phosphorylation stability, which was found to be dependent on a conserved Asp residue (Asp-696) within the kinase receiver domain. Asp-696 also played an important role in defining the specificity of phosphorylation for response regulators CbbRR1 or CbbRR2, and this residue appeared to act in conjunction with residues within the region from Arg-96 to Thr-189 at the N terminus of the sensor kinase. The net effect of concerted interactions at these distinct regions of CbbSR created an internal molecular switch that appears to coordinate a unique branched phosphorelay system.