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101.
Elena SF Bedhomme S Carrasco P Cuevas JM de la Iglesia F Lafforgue G Lalić J Pròsper A Tromas N Zwart MP 《Molecular plant-microbe interactions : MPMI》2011,24(3):287-293
Over the years, agriculture across the world has been compromised by a succession of devastating epidemics caused by new viruses that spilled over from reservoir species or by new variants of classic viruses that acquired new virulence factors or changed their epidemiological patterns. Viral emergence is usually associated with ecological change or with agronomical practices bringing together reservoirs and crop species. The complete picture is, however, much more complex, and results from an evolutionary process in which the main players are ecological factors, viruses' genetic plasticity, and host factors required for virus replication, all mixed with a good measure of stochasticity. The present review puts emergence of plant RNA viruses into the framework of evolutionary genetics, stressing that viral emergence begins with a stochastic process that involves the transmission of a preexisting viral strain into a new host species, followed by adaptation to the new host. 相似文献
102.
Yogan Monnier Bruno Vila Nicolas Mont��s Anne Bousquet-M��lou Bernard Pr��vosto Catherine Fernandez 《Trees - Structure and Function》2011,25(3):497-507
Pinus halepensis Mill., is a Mediterranean pioneer forest species with shade-intolerant features. The purpose of this study is to better understand
how stand fertility and allelopathic properties of adult trees influence shade acclimation of saplings. Crown growth and morphological
plasticity were studied under different light, fertilization, and allelopathic conditions in a nursery experiment. We tested
whether shade-acclimation capacity increases with fertilization, and is affected by autotoxicity due to pine leachates. We
examined stem diameter, and crown characteristics (length, width, shape, and density) in a factorial experiment with two levels
for each tested factor: light (full and 20% reduced light), fertilization (low and high rate of NPK fertilizer) and allelopathy
(control and allelopathic leachates uptake). In our study, shading induced a significantly higher crown length, width, and
surface. Fertilization strongly increased crown length and vertical expended crown shape (the ratio crown length/crown width).
Leachates uptake reduced crown length and density, highlighting an autotoxicity phenomenon. We concluded that P. halepensis saplings presented a shade-avoiding syndrome and that the crown shade-acclimation response increased with fertilization but
was severely compromised by autotoxicity. We finally discuss the role of fertilization and allelopathy in early P. halepensis acclimation ability. 相似文献
103.
Nworah DC Chike CP Akpa MR Nwafor A Dapper DV 《Nigerian journal of physiological sciences》2011,26(1):7-10
This study investigated the prevalence of electrocardiographically determined left ventricular hypertrophy in hypertensive and normotensive type 2 diabetic females who went for consultation at the University of Port Harcourt Teaching Hospital (UPTH), Rivers State, Nigeria. Two hundred participants mean age 52years, attending the medical outpatient clinic over a 6-month period were recruited for the study. Of the population studied, 16.5% of the hypertensive and 13.0% of the normotensive diabetics had left ventricular hypertrophy. Cardiovascular abnormalities notably bifascicular block, left atrial block, right ventricular enlargement, and right atrial enlargement were predominately among hypertensive diabetes and also notably was arrhythmia and atrial flutter among normotensive diabetes. The significance of these findings is discussed. Keywords: Hypertension, Diabetes mellitus, Cardiovascular disease, Left ventricular hypertrophy. 相似文献
104.
Charl��ne Bouchaud Margareta Tengberg Patricia Dal Pr�� 《Vegetation History and Archaeobotany》2011,20(5):405-417
The discovery of seeds and textiles from Gossypium (cotton) in Achaemenian levels of the mid-6th–late 4th century b.c. at Qal’at al-Bahrain, Bahrain and in early 1st millennium a.d. at Mada’in Salih, Saudi Arabia, reveals the role played by the Arabian Peninsula as a textile production centre during the
centuries before and after the beginning of the Christian era. Both these sites were situated on important trade routes, overseas
(Qal’at al-Bahrain) and overland (Mada’in Salih), and it is likely that at least part of the cotton production was intended
for trade, complementing and perhaps competing with other sources of cotton textiles in the contemporary Middle East. In the
arid climate of the Arabian Peninsula, cotton was probably grown in association with irrigated date palm gardens where a wide
array of other crops was grown, as is shown by the analysis of charred seeds and wood from occupation levels at both sites.
The present article places these particular finds in the larger context of cotton cultivation in the Middle East and India. 相似文献
105.
Prévost S Riemer S Fischer W Haag R Böttcher C Gummel J Grillo I Appavou MS Gradzielski M 《Biomacromolecules》2011,12(12):4272-4282
Polyplexes of short DNA-fragments (300 b.p., 100 nm) with tailor-made amine-based polycations of different architectures (linear and hyperbranched) were investigated in buffer solution as a function of the mixing ratio with DNA. The resulting dispersed polyplexes were characterized using small-angle neutron and X-ray scattering (SANS, SAXS) as well as cryo-TEM with respect to their mesoscopic structure and their colloidal stability. The linear polyimines form rather compact structures that have a high tendency for precipitation. In contrast, the hyperbranched polycation with enzymatic-labile pentaethylenehexamine arms (PEHA) yields polyplexes colloidally stable for months. Here the polycation coating of DNA results in a homogeneous dispersion based on a fractal network with low structural organization at low polycation amount. With increasing polycation, bundles of tens of aligned DNA rods appear that are interconnected in a fractal network with a typical correlation distance on the order of 100 nm, the average length of the DNA used. With higher organization comes a decrease in stability. The 3D network built by these beams can still exhibit some stability as long as the material concentration is large enough, but the structure collapses upon dilution. SAXS shows that the complexation does not affect the local DNA structure. Interestingly, the structural findings on the DNA polyplexes apparently correlate with the transfection efficiency of corresponding siRNA complexes. In general, these finding not only show systematic trends for the colloid stability, but may allow for rational approaches to design effective transfection carriers. 相似文献
106.
Johannes Pr?ll Martin Danzer Stephanie Stabentheiner Norbert Niklas Christa Hackl Katja Hofer Sabine Atzmüller Peter Hufnagl Christian Gülly Hanns Hauser Otto Krieger Christian Gabriel 《DNA research》2011,18(4):201-210
How cells coordinate the immune system activities is important for potentially life-saving organ or stem cell transplantations. Polymorphic immunoregulatory genes, many of them located in the human major histocompatibility complex, impact the process and assure the proper execution of tolerance-versus-activity mechanisms. In haematopoietic stem cell transplantation, on the basis of fully human leukocyte antigen (HLA)-matched donor–recipient pairs, adverse effects like graft versus leukaemia and graft versus host are observed and difficult to handle. So far, high-resolution HLA typing was performed with Sanger sequencing, but for methodological reasons information on additional immunocompetent major histocompatibility complex loci has not been revealed. Now, we have used microarray sequence capture and targeted enrichment combined with next generation pyrosequencing for 3.5 million base pair human major histocompatibility complex resequencing in a clinical transplant setting and describe 3025 variant single nucleotide polymorphisms, insertions and deletions among recipient and donor in a single sequencing experiment. Taken together, the presented data show that sequence capture and massively parallel pyrosequencing can be used as a new tool for risk assessment in the setting of allogeneic stem cell transplantation. 相似文献
107.
Buschke S Stark HJ Cerezo A Prätzel-Wunder S Boehnke K Kollar J Langbein L Heldin CH Boukamp P 《Molecular biology of the cell》2011,22(6):782-794
The mechanism by which transforming growth factor-β (TGFβ) regulates differentiation in human epidermal keratinocytes is still poorly understood. To assess the role of Smad signaling, we engineered human HaCaT keratinocytes either expressing small interfering RNA against Smads2, 3, and 4 or overexpressing Smad7 and verified impaired Smad signaling as decreased Smad phosphorylation, aberrant nuclear translocation, and altered target gene expression. Besides abrogation of TGFβ-dependent growth inhibition in conventional cultures, epidermal morphogenesis and differentiation in organotypic cultures were disturbed, resulting in altered tissue homeostasis with suprabasal proliferation and hyperplasia upon TGFβ treatment. Neutralizing antibodies against TGFβ, similar to blocking the actions of EGF-receptor or keratinocyte growth factor, caused significant growth reduction of Smad7-overexpressing cells, thereby demonstrating that epithelial hyperplasia was attributed to TGFβ-induced "dermis"-derived growth promoting factors. Furthermore impaired Smad signaling not only blocked the epidermal differentiation process or caused epidermal-to-mesenchymal transition but induced a switch to a complex alternative differentiation program, best characterized as mucous/intestinal-type epithelial differentiation. As the same alternative phenotype evolved from both modes of Smad-pathway interference, and reduction of Smad7-overexpression caused reversion to epidermal differentiation, our data suggest that functional TGFβ/Smad signaling, besides regulating epidermal tissue homeostasis, is not only essential for terminal epidermal differentiation but crucial in programming different epithelial differentiation routes. 相似文献
108.
Bernard Prévosto Anne Bousquet-Mélou Christian Ripert Catherine Fernandez 《Plant Ecology》2011,212(4):627-638
Biodiversity maintenance is a key component of Mediterranean forest management, yet studies on the effects of silvicultural
treatments on plant diversity are scarce. Our experiment assessed the impact of five different site preparation treatments
on the composition, diversity, ecological traits (life-form, pollination mode, leaf morphology, seed dispersal mode), indicator
values (shade tolerance, nutrients demand) of the understory vegetation in a mature thinned Pinus halepensis stand in southern France. The treatments—chopping, chopping followed by scarification in one or two directions, prescribed
burning, control—were replicated four times and applied on a total of 40 plots. Vegetation relevés were performed on each
plot in the first, second and fourth year following treatment applications. Plant diversity, measured by the species richness
or Shannon’s index, increased in the non-control treatment plots in the first year but then decreased through time. Vegetation
composition differed between treatments, with the chopping treatment exhibiting composition and ecological trait values more
comparable to those of control plots than the other treatments. The burning and scarification treatments led to higher abundance
of therophytes, plants with malacophyllous leaves and insect-pollinated plants, and shade-intolerant and nutrient-demanding
species. However, these changes were transient in time, the shade-intolerant species remained abundant but the ruderal species
decreased while the ligneous species increased indicating a gradual return to a forest vegetation composition. For the Mediterranean
area, most of the findings were similar to those in temperate forests subjected to the same site preparation treatments. 相似文献
109.
Noll GA Müller B Ernst AM Rüping B Groscurth S Twyman RM Kawchuk LM Prüfer D 《Bioengineered bugs》2011,2(2):111-114
Forisomes are protein bodies found exclusively in the phloem of the Fabaceae (legumes). In response to wounding, the influx of Ca ( 2+) induces a conformational change from a condensed to a dispersed state which plugs the sieve tubes and prevents the loss of photoassimilates. This reversible, ATP-independent reaction can be replicated with purified forisomes in vitro by adding divalent cations or electrically inducing changes in pH, making forisomes ideal components of technical devices. Although native forisomes comprise several subunits, we recently showed that functional homomeric forisomes with distinct properties can be expressed in plants and yeast, providing an abundant supply of forisomes with tailored properties. Forisome subunits MtSEO-F1 and MtSEO-F4 can each assemble into homomeric artificial forisomes, which indicates functional redundancy. However, we provide further evidence that both proteins are subunits of the native heteromeric forisome body in planta. We also show that the properties of artificial forisomes can be modified by immobilization, which is a prerequisite for their incorporation into technical devices. 相似文献
110.
Lengagne R Pommier A Caron J Douguet L Garcette M Kato M Avril MF Abastado JP Bercovici N Lucas B Prévost-Blondel A 《PloS one》2011,6(5):e20235
Tumors affect myelopoeisis and induce the expansion of myeloid cells with immunosuppressive activity. In the MT/ret model of spontaneous metastatic melanoma, myeloid cells are the most abundant tumor infiltrating hematopoietic population and their proportion is highest in the most aggressive cutaneous metastasis. Our data suggest that the tumor microenvironment favors polarization of myeloid cells into type 2 cells characterized by F4/80 expression, a weak capacity to secrete IL-12 and a high production of arginase. Myeloid cells from tumor and spleen of MT/ret mice inhibit T cell proliferation and IFNγ secretion. Interestingly, T cells play a role in type 2 polarization of myeloid cells. Indeed, intra-tumoral myeloid cells from MT/ret mice lacking T cells are not only less suppressive towards T cells than corresponding cells from wild-type MT/ret mice, but they also inhibit more efficiently melanoma cell proliferation. Thus, our data support the existence of a vicious circle, in which T cells may favor cancer development by establishing an environment that is likely to skew myeloid cell immunity toward a tumor promoting response that, in turn, suppresses immune effector cell functions. 相似文献