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11.
Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests 总被引:2,自引:0,他引:2
Andreas Rigling Christof Bigler Britta Eilmann Elisabeth Feldmeyer‐Christe Urs Gimmi Christian Ginzler Ulrich Graf Philipp Mayer Giorgio Vacchiano Pascale Weber Thomas Wohlgemuth Roman Zweifel Matthias Dobbertin 《Global Change Biology》2013,19(1):229-240
An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner‐Alpine regions, the species composition in low elevation forests is changing: The sub‐boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub‐Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger‐scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed‐effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small‐diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services. 相似文献
12.
Ivana Sreckovic Ruth Birner-Gruenberger Britta Obrist Tatjana Stojakovic Hubert Scharnagl Michael Holzer Monika Scholler Sonia Philipose Gunther Marsche Uwe Lang Gernot Desoye Christian Wadsack 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2013,1831(4):737-746
In human high-density lipoprotein (HDL) represents the major cholesterol carrying lipoprotein class in cord blood, while cholesterol is mainly carried by low-density lipoprotein in maternal serum. Additionally, to carrying cholesterol, HDL also associates with a range of proteins as cargo. We tested the hypothesis that fetal HDL carries proteins qualitatively and quantitatively different from maternal HDL. These differences then contribute to distinct HDL functionality in both circulations. Shotgun proteomics and biochemical analyses were used to assess composition/function of fetal and maternal HDL isolated from uncomplicated human pregnancies at term of gestation. The pattern of analyzed proteins that were statistically elevated in fetal HDL (apoE, proteins involved in coagulation, transport processes) suggests a particle characteristic for the light HDL2 sub-fraction. In contrast, proteins that were enriched in maternal HDL (apoL, apoF, PON1, apoD, apoCs) have been described almost exclusively in the dense HDL3 fraction and relevant to its anti-oxidative function and role in innate immunity. Strikingly, PON1 mass and activity were 5-fold lower (p < 0.01) in the fetus, which was accompanied by attenuation of anti-oxidant capacity of fetal HDL. Despite almost equal quantity of CETP in maternal and fetal HDL, its enzymatic activity was 55% lower (p < 0.001) in the fetal circulation, whereas LCAT activity was not altered. These findings indicate that maternally derived HDL differs from fetal HDL with respect to its proteome, size and function. Absence of apoA-1, apoL and PON1 on fetal HDL is associated with decreased anti-oxidative properties together with deficiency in innate immunity collectively indicating distinct HDLs in fetuses. 相似文献
13.
Ly Lindman Britta Johansson Karl Gotthard Toomas Tammaru 《Journal of Insect Conservation》2013,17(2):375-383
The aim of the present study was to evaluate—in a geographic perspective—the role of host plant as a determinant of habitat quality for Lopinga achine, a satyrine butterfly endangered over much of its European range. Laboratory trials were performed to record host choices made by the ovipositing females as well as by neonate larvae. In rearing experiments, growth performance and mortality on different host plants was determined. Oviposition was found to be indiscriminate but larvae were shown to be able to choose between host plants, with the choices made broadly consistent with growth performance of the larvae on particular hosts. Nevertheless, most grasses and sedges offered were found to support larval development reasonably well. No clear superiority of the previously suggested primary host plant Carex montana could be shown. Importantly, no differences in host plant relationships were found between the populations of Sweden, western Estonia and eastern Estonia. In particular, the larvae originating from eastern Estonian populations developed on C. montana equally well even if the plant is absent from their native habitat. In the context of species conservation, one should conclude that L. achine is polyphagous enough on various grasses and sedges so that the presence of any particular host species cannot be a critical component of habitat quality. Nevertheless, some preference to broad- and soft-leaved hosts, as well as sensitivity to host wilting, may partly explain the butterfly’s preference to moist forest habitats, further emphasizing the central role of habitat management in the conservation practice of this species. In turn, the absence of ecological differences between geographic populations should enable conservationists to successful transfer their experience across national boundaries. 相似文献
14.
Frank Adolf Alexia Herrmann Andrea Hellwig Rainer Beck Britta Brügger Felix T. Wieland 《Traffic (Copenhagen, Denmark)》2013,14(8):922-932
Intracellular transport and maintenance of the endomembrane system in eukaryotes depends on formation and fusion of vesicular carriers. A seeming discrepancy exists in the literature about the basic mechanism in the scission of transport vesicles that depend on GTP‐binding proteins. Some reports describe that the scission of COP‐coated vesicles is dependent on GTP hydrolysis, whereas others found that GTP hydrolysis is not required. In order to investigate this pivotal mechanism in vesicle formation, we analyzed formation of COPI‐ and COPII‐coated vesicles utilizing semi‐intact cells. The small GTPases Sar1 and Arf1 together with their corresponding coat proteins, the Sec23/24 and Sec13/31 complexes for COPII and coatomer for COPI vesicles were required and sufficient to drive vesicle formation. Both types of vesicles were efficiently generated when GTP hydrolysis was blocked either by utilizing the poorly hydrolyzable GTP analogs GTPγS and GMP‐PNP, or with constitutively active mutants of the small GTPases. Thus, GTP hydrolysis is not required for the formation and release of COP vesicles. 相似文献
15.
Carola E. Bunse Sylvia Borchers Pavankumar R. Varanasi Sabine Tischer Constan?a Figueiredo Stephan Immenschuh Ulrich Kalinke Ulrike K?hl Lilia Goudeva Britta Maecker-Kolhoff Arnold Ganser Rainer Blasczyk Eva M. Weissinger Britta Eiz-Vesper 《PloS one》2013,8(12)
Adoptive transfer of antiviral T cells enhances immune reconstitution and decreases infectious complications after stem cell transplantation. Information on number and function of antiviral T cells in stem cell grafts is scarce. We investigated (1) immunomodulatory effects of G-CSF on antiviral T cells, (2) the influence of apheresis, and (3) the optimal time point to collect antiviral cells.CMV-, EBV- and ADV-specific T cells were enumerated in 170 G-CSF-mobilized stem cell and 24 non-mobilized platelet donors using 14 HLA-matched multimers. T-cell function was evaluated by IFN-γ ELISpot and granzyme B secretion. Immunophenotyping was performed by multicolor flow cytometry.G-CSF treatment did not significantly influence frequency of antiviral T cells nor their in vitro expansion rate upon antigen restimulation. However, T-cell function was significantly impaired, as expressed by a mean reduction in secretion of IFN-γ (75% in vivo, 40% in vitro) and granzyme B (32% target-independent, 76% target-dependent) as well as CD107a expression (27%). Clinical follow up data indicate that the first CMV-reactivation in patients and with it the need for T-cell transfer occurs while the donor is still under the influence of G-CSF.To overcome these limitations, T-cell banking before mobilization or recruitment of third party donors might be an option to optimize T-cell production. 相似文献
16.
Matthias Hardtke-Wolenski Lilli Kraus Christel Schmetz Britta Trautewig Fatih Noyan Florian W. R. Vondran Hueseyin Bektas Juergen Klempnauer Elmar Jaeckel Thorsten Lieke 《PloS one》2013,8(10)
Background
T cells are known to participate in the response to tumor cells and react with cytotoxicity and cytokine release. At the same time tumors established versatile mechanisms for silencing the immune responses. The interplay is far from being completely understood. In this study we show contacts between tumor cells and lymphocytes revealing novel characteristics in the interaction of T cells and cancer cells in a way not previously described.Methods/ Findings
Experiments are based on the usage of a hydrophilic fluorescent dye that occurs free in the cytosol and thus transfer of fluorescent cytosol from one cell to the other can be observed using flow cytometry. Tumor cells from cell lines of different origin or primary hepatocellular carcinoma (HCC) cells were incubated with lymphocytes from human and mice. This exposure provoked a contact dependent uptake of tumor derived cytosol by lymphocytes – even in CD4+ T cells and murine B cells – which could not be detected after incubation of lymphocytes with healthy cells. The interaction was a direct one, not requiring the presence of accessory cells, but independent of cytotoxicity and TCR engagement.Electron microscopy disclosed 100-200nm large gaps in the cell membranes of connected cells which separated viable and revealed astonishing outcome. While the lymphocytes were induced to proliferate in a long term fashion, the tumor cells underwent a temporary break in cell division. The in vitro results were confirmed in vivo using a murine acute lymphoblastic leukemia (ALL) model. The arrest of tumor proliferation resulted in a significant prolonged survival of challenged mice.Conclusions
The reported cell-cell contacts reveal new characteristics i.e. the enabling of cytosol flow between the cells including biological active proteins that influence the cell cycle and biological behaviour of the recipient cells. This adds a completely new aspect in tumor induced immunology. 相似文献17.
Britta Johansen Christian Uhrenfeldt Arne Nylandsted Larsen 《Plasmonics (Norwell, Mass.)》2013,8(1):153-158
This work investigates the localized surface plasmon resonance (LSPR) of β-Sn also known as white tin. Recently, studies on arrays of β-Sn nanoparticles have shown that these arrays possess strong optical features caused by diffractive effects in the particle grating (Johansen et al., Phys Rev B 84:113405–113408, 2011). In the presence of the grating, the LSPR could not clearly be distinguished in the spectra. To get a better understanding of the plasmonic properties of the particles, we have now eliminated the diffractive effects by placing the particles in a random distribution. The particles were fabricated by electron beam lithography on a fused silica substrate and investigated by optical transmission measurements. In the random configuration, a clear LSPR is observed at 530 nm for particles with a diameter of 155 nm and a height of 50 nm. 相似文献
18.
Mukhran Khundadze Katrin Kollmann Nicole Koch Christoph Biskup Sandor Nietzsche Geraldine Zimmer J. Christopher Hennings Antje K. Huebner Judit Symmank Amir Jahic Elena I. Ilina Kathrin Karle Ludger Sch?ls Michael Kessels Thomas Braulke Britta Qualmann Ingo Kurth Christian Beetz Christian A. Hübner 《PLoS genetics》2013,9(12)
Hereditary spastic paraplegias (HSPs) are characterized by progressive weakness and spasticity of the legs because of the degeneration of cortical motoneuron axons. SPG15 is a recessively inherited HSP variant caused by mutations in the ZFYVE26 gene and is additionally characterized by cerebellar ataxia, mental decline, and progressive thinning of the corpus callosum. ZFYVE26 encodes the FYVE domain-containing protein ZFYVE26/SPASTIZIN, which has been suggested to be associated with the newly discovered adaptor protein 5 (AP5) complex. We show that Zfyve26 is broadly expressed in neurons, associates with intracellular vesicles immunopositive for the early endosomal marker EEA1, and co-fractionates with a component of the AP5 complex. As the function of ZFYVE26 in neurons was largely unknown, we disrupted Zfyve26 in mice. Zfyve26 knockout mice do not show developmental defects but develop late-onset spastic paraplegia with cerebellar ataxia confirming that SPG15 is caused by ZFYVE26 deficiency. The morphological analysis reveals axon degeneration and progressive loss of both cortical motoneurons and Purkinje cells in the cerebellum. Importantly, neuron loss is preceded by accumulation of large intraneuronal deposits of membrane-surrounded material, which co-stains with the lysosomal marker Lamp1. A density gradient analysis of brain lysates shows an increase of Lamp1-positive membrane compartments with higher densities in Zfyve26 knockout mice. Increased levels of lysosomal enzymes in brains of aged knockout mice further support an alteration of the lysosomal compartment upon disruption of Zfyve26. We propose that SPG15 is caused by an endolysosomal membrane trafficking defect, which results in endolysosomal dysfunction. This appears to be particularly relevant in neurons with highly specialized neurites such as cortical motoneurons and Purkinje cells. 相似文献
19.
Patricia Kreis Rita Hendricusdottir Louise Kay Ismini E. Papageorgiou Michiel van Diepen Till Mack Jonny Ryves Adrian Harwood Nicholas R. Leslie Oliver Kann Maddy Parsons Britta J. Eickholt 《PloS one》2013,8(8)
Defects in actin dynamics affect activity-dependent modulation of synaptic transmission and neuronal plasticity, and can cause cognitive impairment. A salient candidate actin-binding protein linking synaptic dysfunction to cognitive deficits is Drebrin (DBN). However, the specific mode of how DBN is regulated at the central synapse is largely unknown. In this study we identify and characterize the interaction of the PTEN tumor suppressor with DBN. Our results demonstrate that PTEN binds DBN and that this interaction results in the dephosphorylation of a site present in the DBN C-terminus - serine 647. PTEN and pS647-DBN segregate into distinct and complimentary compartments in neurons, supporting the idea that PTEN negatively regulates DBN phosphorylation at this site. We further demonstrate that neuronal activity increases phosphorylation of DBN at S647 in hippocampal neurons in vitro and in ex vivo hippocampus slices exhibiting seizure activity, potentially by inducing rapid dissociation of the PTEN:DBN complex. Our results identify a novel mechanism by which PTEN is required to maintain DBN phosphorylation at dynamic range and signifies an unusual regulation of an actin-binding protein linked to cognitive decline and degenerative conditions at the CNS synapse. 相似文献
20.
Kendall A. West Eckhard W. Heymann Britta Mueller Thomas R. Gillespie 《International journal of primatology》2013,34(5):939-945
Recent evidence of pathogen transmission to humans from wild primates and a greater recognition of the risk of human pathogen transmission to free-ranging primates have raised awareness of the potential impact of zoonotic pathogen transmission on primate conservation and nonhuman primate and human health. Cryptosporidium and Giardia are zoonotic protozoan parasites transmitted via fecal–oral contamination or water that can cause gastritis or enteritis in human and nonhuman primates. From June 2002 to September 2003, we collected fecal samples noninvasively from two species of tamarins (Saguinus mystax and S. nigrifrons) and one species of titi monkeys (Callicebus cupreus) at the Estación Biológica Quebrada Blanco in the Peruvian Amazon to determine the distribution and prevalence of these potential pathogens. We screened 140 fecal samples representing known individuals of each species for Cryptosporidium and Giardia using the Merifluor immunoflourescence assay to determine the prevalence and intensity of infection with these organisms. With the exception of two samples we collected during the same week from a juvenile male Saguinus mystax, all samples were negative for Cryptosporidium. None of the fecal samples were positive for Giardia. The low prevalence of infection we observed limited our ability to examine the effects of demographic and environmental variables on patterns of infection; however, the exceptionally low prevalence of Cryptosporidium suggests that it is not a current health threat to these primate populations. Although the origin of infection with Cryptosporidium in the juvenile male Saguinus mystax cannot be determined, its presence alerts us to the potential for cross-species transmission and highlights the need for more detailed research to improve our understanding of the distribution and diversity of potentially pathogenic protozoa in Neotropical primate populations. 相似文献