Large-scale identification of leaf senescence-associated genes

Leaf senescence is a form of programmed cell death, and is believed to involve preferential expression of a specific set of "senescence-associated genes" (SAGs). To decipher the molecular mechanisms and the predicted complex network of regulatory pathways involved in the senescence program, we have carried out a large-scale gene identification study in a reference plant, Arabidopsis thaliana. Using suppression subtractive hybridization, we isolated approximately 800 cDNA clones representing SAGs expressed in senescing leaves. Differential expression was confirmed by Northern blot analysis for 130 non-redundant genes. Over 70 of the identified genes have not previously been shown to participate in the senescence process. SAG-encoded proteins are likely to participate in macromolecule degradation, detoxification of oxidative metabolites, induction of defense mechanisms, and signaling and regulatory events. Temporal expression profiles of selected genes displayed several distinct patterns, from expression at a very early stage, to the terminal phase of the senescence syndrome. Expression of some of the novel SAGs, in response to age, leaf detachment, darkness, and ethylene and cytokinin treatment was compared. The large repertoire of SAGs identified here provides global insights about regulatory, biochemical and cellular events occurring during leaf senescence.     

Important differences in nitric oxide synthase activity and predominant isoform in reproductive tissues from human and rat

For the extrapolation of data obtained from experimental animals to the human situation, it is important to know the similarities and differences between human and animal species. Some important characteristics of nitric oxide synthase (NOS) in myometrium and vagina from human and rat were compared. NOS-activity was measured by the formation of ¹⁴C-citrulline from ¹⁴C-arginine and the expression of NOS isoforms was examined by Western blotting. NOS activity in human uterus and vagina was significantly lower than in the tissues from rat. In contrast to the rat where NOS activity was predominantly found in the cytosolic fractions, NOS activity in particulate and cytosolic fractions from both human myometrium and vagina was similar. Data from Western blots confirmed that eNOS and nNOS isoforms were concentrated in the particulate and cytosolic fractions, respectively. Estrogen treatment of rats resulted in a down regulation of uterine cytosolic NOS activity. A down regulation of NOS in the cytosolic fraction was also seen in the human pregnant myometrium as compared with the nonpregnant myometrium. The vaginal NOS activity was considerably higher than the uterus in both species. In spite of some clear-cut qualitative and other differences between human and rat tissues, there are some interesting similarities. Downregulation in pregnancy of human uterine NOS is probably due to, at least in part, the influence of estrogen and progesterone.     

Biodistribution study of nanometric hybrid gadolinium oxide particles as a multimodal SPECT/MR/optical imaging and theragnostic agent

Nanometric hybrid gadolinium oxide particles (Gado-6Si-NP) for diagnostic and therapeutic applications (mean diameter 3-4 nm) were obtained by encapsulating Gd(2)O(3) cores within a polysiloxane shell, which carries organic fluorophore (Cy 5) and is derivatized by a hydrophilic carboxylic layer. As residency time in the living body and methods of waste elimination are crucial to defining a good nanoparticle candidate and moving forward with steps for validation, this study was aimed at evaluating the biodistribution of these multimodal Gado-6Si-NP in rodents. Gado-6Si-NP were imaged following intravenous injection in control Wistar rats and mice using MRI (7 T), optical fluorescent imaging, and SPECT. A clear correlation was observed among MRI, optical imaging, and SPECT regarding the renal elimination. Quantitative biodistribution using gamma-counting of each sampled organ confirmed that these nanoparticles circulated freely in the blood pool and were rapidly cleared by renal excretion without accumulation in liver and RES uptake. These results demonstrate that Gado-6Si-NP display optimal biodistribution properties, enabling them to be developed as multimodal agents for in vivo imaging and theragnostics, especially in oncological applications.     

Neurosteroid dehydroepiandrosterone interacts with nerve growth factor (NGF) receptors, preventing neuronal apoptosis

The neurosteroid dehydroepiandrosterone (DHEA), produced by neurons and glia, affects multiple processes in the brain, including neuronal survival and neurogenesis during development and in aging. We provide evidence that DHEA interacts with pro-survival TrkA and pro-death p75(NTR) membrane receptors of neurotrophin nerve growth factor (NGF), acting as a neurotrophic factor: (1) the anti-apoptotic effects of DHEA were reversed by siRNA against TrkA or by a specific TrkA inhibitor; (2) [(3)H]-DHEA binding assays showed that it bound to membranes isolated from HEK293 cells transfected with the cDNAs of TrkA and p75(NTR) receptors (K(D): 7.4 ± 1.75 nM and 5.6 ± 0.55 nM, respectively); (3) immobilized DHEA pulled down recombinant and naturally expressed TrkA and p75(NTR) receptors; (4) DHEA induced TrkA phosphorylation and NGF receptor-mediated signaling; Shc, Akt, and ERK1/2 kinases down-stream to TrkA receptors and TRAF6, RIP2, and RhoGDI interactors of p75(NTR) receptors; and (5) DHEA rescued from apoptosis TrkA receptor positive sensory neurons of dorsal root ganglia in NGF null embryos and compensated NGF in rescuing from apoptosis NGF receptor positive sympathetic neurons of embryonic superior cervical ganglia. Phylogenetic findings on the evolution of neurotrophins, their receptors, and CYP17, the enzyme responsible for DHEA biosynthesis, combined with our data support the hypothesis that DHEA served as a phylogenetically ancient neurotrophic factor.     

Environmental factors determining regional biodiversity patterns of groundwater fauna in semi-arid aquifers of northwest Algeria

Limnology - This study investigated the biodiversity and hydrochemistry of seven unconfined aquifers located in two hydrogeological complexes in the north-western region of Algeria. The aim of the...     

Amphibian decline,pond loss and reduced population connectivity under agricultural intensification over a 38 year period

Habitat loss, together with less obvious land-use changes such as intensified farming practice, can have significant adverse impacts on biodiversity. An important factor in determining the ability of species to cope with such changes is their potential to sustain a populations network by dispersal across the landscape. Habitat quality and structure are particularly important for surface-dwelling species with low dispersal abilities, such as amphibians. To assess this ecological function, ponds in a coastal and typically rural area of northern France were surveyed for amphibians in 1974, 1992 and 2011. These repeated surveys yielded different outcomes for different species groups. Three rare species persisted in more or less specialized habitat types. Two moderately common species declined, but kept strongholds in coastal dunes and associated marshes. Five common species with broad ecological niches remained equally widespread. The Northern crested newt declined markedly and the Midwife toad declined dramatically, as did their breeding habitats in vegetated ponds and cattle drinking troughs. One species, the Moor frog, may have gone locally extinct. A model of relative resistance to amphibian dispersal was created for different landscape types, on a scale from 0 (low resistance) to 1 (high resistance). This generated values of 0.23 for pasture, 0.72 for arable and 0.98 for urban and transport. As pasture declined in the study area, while arable and urban/transport infrastructure increased, amphibian dispersal became more difficult. However, dispersal paths proved difficult to evaluate in a patchy landscape like the one surveyed, due to a paucity of spatial signal. Pond loss is a more tractable reason for the observed amphibian species decline than is the quality of intervening terrestrial habitat matrix. In 2011, 22 newly created ponds had species richness in line with pre-existing ponds and this will have counteracted a dwindling metapopulation structure, indicating that habitat creation/restoration can play a valuable role in conservation. The colonization of new ponds may also prove more informative for gauging the potential for amphibian dispersal in the landscape than the preceding decline.     

The O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status and clinical outcomes of Ewing sarcoma patients treated with irinotecan and temozolomide

BackgroundThere remains an unmet need to identify molecular biomarkers in Ewing sarcoma (ES). We sought to assess the influence of the O⁶-methylguanine-DNA methyltransferase (MGMT) promoter methylation on response and progression-free survival (PFS) following initiation of irinotecan and temozolomide (IT), PFS following initiation of vincristine, doxorubicin, and cyclophosphamide alternating with ifosfamide and etoposide (VDC-IE), and overall survival (OS).Materials and methodsData of advanced ES patients, treated with IT were retrospectively collected. Patients were required to have progression after prior VDC-IE. MGMT promoter methylation was assessed on non-decalcified Formalin-fixed paraffin embedded (FFPE) tissue using methylation sensitive restriction enzyme-quantitative PCR (MSRE-qPCR). Survival was estimated by the Kaplan-Meier method.ResultsA total of 20 ES patients underwent MGMT promoter methylation testing, and were eligible for analysis. Five patients (25%) had methylated MGMT, whereas the remaining (15; 75%) had unmethylated promoter. Five (25%) had objective response to IT, with no observed difference by promoter methylation (p = 0.76). Median PFS from initiation of IT for methylated vs. unmethylated MGMT patients was 4.9 and 1.2 months, respectively, p = 0.69. Median PFS from date of initiation of VDC-IE was significantly superior in the methylated group; 27.8 vs. 8.6 months, p = 0.034. Median OS was superior but not statistically significant in the methylated group.ConclusionMGMT-promoter methylation did not correlate with clinical activity or outcomes following the IT regimen for advanced ES. However, methylated MGMT predicted significantly superior PFS following initiation of the standard VDC-IE protocol.     

Investigation of lipid production by nitrogen-starved <Emphasis Type="Italic">Parachlorella kessleri</Emphasis> under continuous illumination and day/night cycles for biodiesel application

This study aims to investigate the triacylglycerol (TAG) productivity of Parachlorella kessleri grown under continuous illumination and to investigate its metabolism in simulated day/night cycles in order to estimate the feasibility of a large-scale production in outdoor solar photobioreactors. The strain was chosen for its ability to accumulate large amounts of triacylglycerol during nitrogen starvation. Several protocols of nitrogen starvation were tested in continuous illumination as well as in simulated day/night cycles. Sudden and progressive nitrogen starvation conditions have enhanced the TAG concentration and productivity of P. kessleri reaching up to 48 dry wt% and 4.4 × 10^?3 kg m^?2 day^?1, respectively. Microalgal cell metabolism was significantly affected by the day/night illumination cycles. The energy-rich compounds (TAGs and carbohydrates) were accumulated by P. kessleri during the photoperiods and partly consumed during the dark to sustain the microalgae vitality. This TAG oxidation ultimately led to a 26% decrease in TAG productivity in cultures exposed to day/night cycles compared to ones exposed to continuous illumination of equal 24-h average photon flux density. The results can dictate the optimal time for harvesting cells for recovering the largest amount of TAGs.     

Unraveling persistent host cell infection with Coxiella burnetii by quantitative proteomics

The interaction between the immune system and invading bacteria is sufficient to eradicate microorganisms for the majority of bacterial infections, but suppression of the microbicidal response leads to reactivation or chronic evolution of infections and to bacterial persistence. To identify the cellular pathways affected by bacterial persistence, we applied the MS-driven combined fractional diagonal chromatography (COFRADIC) proteomics technique for a comparative study of protein expression in the C. burnetii strains Nine Mile (NM) and its respective strain (NMper) isolated from 18 months persistently infected cell cultures. In total, three different proteome comparisons were performed with the total bacterial proteome, potentially secreted bacterial proteins, and the eukaryotic infected proteome being assessed. Our results revealed that among the 547 identified bacterial proteins, 53 had significantly altered levels of expression and indicated potential metabolic differences between the two strains. Regarding differences in the secreted proteins between both strains and different modulation of the host cell, machineries reflect at least large rearrangements of both bacterial and eukaryotic proteomes during the persistent model of infection when compared to the acute one, which emphasizes that C. burnetii orchestrates a vast number of different bacterial and eukaryotic host cell processes to persist within its host.