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Search Results: 1 - 10 of 17865 matches for " Mark Tackenberg "
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Versatile and Simple Approach to Determine Astrocyte Territories in Mouse Neocortex and Hippocampus
Antje Grosche, Jens Grosche, Mark Tackenberg, Dorit Scheller, Gwendolyn Gerstner, Annett Gumprecht, Thomas Pannicke, Petra G. Hirrlinger, Ulrika Wilhelmsson, Kerstin Hüttmann, Wolfgang H?rtig, Christian Steinh?user, Milos Pekny, Andreas Reichenbach
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069143
Abstract: Background Besides their neuronal support functions, astrocytes are active partners in neuronal information processing. The typical territorial structure of astrocytes (the volume of neuropil occupied by a single astrocyte) is pivotal for many aspects of glia–neuron interactions. Methods Individual astrocyte territorial volumes are measured by Golgi impregnation, and astrocyte densities are determined by S100β immunolabeling. These data are compared with results from conventionally applied methods such as dye filling and determination of the density of astrocyte networks by biocytin loading. Finally, we implemented our new approach to investigate age-related changes in astrocyte territories in the cortex and hippocampus of 5- and 21-month-old mice. Results The data obtained by our simplified approach based on Golgi impregnation were compared to previously published dye filling experiments, and yielded remarkably comparable results regarding astrocyte territorial volumes. Moreover, we found that almost all coupled astrocytes (as indicated by biocytin loading) were immunopositive for S100β. A first application of this new experimental approach gives insight in age-dependent changes in astrocyte territorial volumes. They increased with age, while cell densities remained stable. In 5-month-old mice, the overlap factor was close to 1, revealing little or no interdigitation of astrocyte territories. However, in 21-month-old mice, the overlap factor was more than 2, suggesting that processes of adjacent astrocytes interdigitate. Conclusion Here we verified the usability of a simple, versatile method for assessing astrocyte territories and the overlap factor between adjacent territories. Second, we found that there is an age-related increase in territorial volumes of astrocytes that leads to loss of the strict organization in non-overlapping territories. Future studies should elucidate the physiological relevance of this adaptive reaction of astrocytes in the aging brain and the methods presented in this study might be a powerful tool to do so.
Are Plant Species Able to Keep Pace with the Rapidly Changing Climate?
Sarah Cunze, Felix Heydel, Oliver Tackenberg
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067909
Abstract: Future climate change is predicted to advance faster than the postglacial warming. Migration may therefore become a key driver for future development of biodiversity and ecosystem functioning. For 140 European plant species we computed past range shifts since the last glacial maximum and future range shifts for a variety of Intergovernmental Panel on Climate Change (IPCC) scenarios and global circulation models (GCMs). Range shift rates were estimated by means of species distribution modelling (SDM). With process-based seed dispersal models we estimated species-specific migration rates for 27 dispersal modes addressing dispersal by wind (anemochory) for different wind conditions, as well as dispersal by mammals (dispersal on animal's coat – epizoochory and dispersal by animals after feeding and digestion – endozoochory) considering different animal species. Our process-based modelled migration rates generally exceeded the postglacial range shift rates indicating that the process-based models we used are capable of predicting migration rates that are in accordance with realized past migration. For most of the considered species, the modelled migration rates were considerably lower than the expected future climate change induced range shift rates. This implies that most plant species will not entirely be able to follow future climate-change-induced range shifts due to dispersal limitation. Animals with large day- and home-ranges are highly important for achieving high migration rates for many plant species, whereas anemochory is relevant for only few species.
Range Expansion of Ambrosia artemisiifolia in Europe Is Promoted by Climate Change
Sarah Cunze,Marion Carmen Leiblein,Oliver Tackenberg
ISRN Ecology , 2013, DOI: 10.1155/2013/610126
Abstract: Ambrosia artemisiifolia L., native to North America, is a problematic invasive species, because of its highly allergenic pollen. The species is expected to expand its range due to climate change. By means of ecological niche modelling (ENM), we predict habitat suitability for A. artemisiifolia in Europe under current and future climatic conditions. Overall, we compared the performance and results of 16 algorithms commonly applied in ENM. As occurrence records of invasive species may be dominated by sampling bias, we also used data from the native range. To assess the quality of the modelling approaches we assembled a new map of current occurrences of A. artemisiifolia in Europe. Our results show that ENM yields a good estimation of the potential range of A. artemisiifolia in Europe only when using the North American data. A strong sampling bias in the European Global Biodiversity Information Facility (GBIF) data for A. artemisiifolia causes unrealistic results. Using the North American data reflects the realized European distribution very well. All models predict an enlargement and a northwards shift of potential range in Central and Northern Europe during the next decades. Climate warming will lead to an increase and northwards shift of A. artemisiifolia in Europe. 1. Introduction Ambrosia artemisiifolia L. (common ragweed), native to North America, is considered as one of the most problematic invasive species in Europe (e.g., [1]). The species produces highly allergenic pollen in huge amounts (e.g., [2]). Up to 12% of the human population suffers from allergy (rhinitis and asthma) to Ambrosia pollen [3]. The medical costs of people with allergies are enormous (e.g., [3]) and will increase in case of a further spread of A. artemisiifolia in Europe. The invasion of A. artemisiifolia into Europe proceeded in two stages: (1) A. artemisiifolia was inadvertently introduced into Europe in the 19th century and has become a widespread alien species in South-eastern Europe [4]. (2) In the last decade many expanding populations of A. artemisiifolia in Central and Northern Europe have been evidenced [5]. Climate change and invasive species are regarded as major threats to biodiversity (e.g., [6, 7]). Invasive species may induce economic problems, particularly in agriculture and forestry [7]. When considering A. artemisiifolia, the main problem is the health risk for human population. Some invasive species may be promoted by climate change (e.g., [8]) due to characteristics that facilitate rapid range shifts (e.g., short time to maturity and low seed mass) and due
MK2 and Fas Receptor Contribute to the Severity of CNS Demyelination
Silvia M. Tietz, Regina Hofmann, Tobias Thomas, Bj?rn Tackenberg, Matthias Gaestel, Martin Berghoff
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100363
Abstract: Models of inflammatory or degenerative diseases demonstrated that the protein-kinase MK2 is a key player in inflammation. In this study we examined the role of MK2 in MOG35-55-induced experimental autoimmune encephalomyelitis (EAE), the animal model for multiple sclerosis. In MK2-deficient (MK2?/?) mice we found a delayed onset of the disease and MK2?/? mice did not recover until day 24 after EAE induction. At this day a higher number of leukocytes in the CNS of MK2?/? mice was found. TNFα was not detectable in serum of MK2?/? mice in any stage of EAE, while high TNFα levels were found at day 16 in wild-type mice. Further investigation revealed an increased expression of FasR mRNA in leukocytes isolated from CNS of wild-type mice but not in MK2?/? mice, however in vitro stimulation of MK2?/? splenocytes with rmTNFα induced the expression of FasR. In addition, immunocomplexes between the apoptosis inhibitor cFlip and the FasR adapter molecule FADD were only detected in splenocytes of MK2?/? mice at day 24 after EAE induction. Moreover, the investigation of blood samples from relapsing-remitting multiple sclerosis patients revealed reduced FasR mRNA expression compared to healthy controls. Taken together, our data suggest that MK2 is a key regulatory inflammatory cytokines in EAE and multiple sclerosis. MK2?/? mice showed a lack of TNFα and thus might not undergo TNFα-induced up-regulation of FasR. This may prevent autoreactive leukocytes from apoptosis and may led to prolonged disease activity. The findings indicate a key role of MK2 and FasR in the regulation and limitation of the immune response in the CNS.
Giant Molecular Filaments in the Milky Way
Sarah E. Ragan,Thomas Henning,Jochen Tackenberg,Henrik Beuther,Katharine G. Johnston,Jouni Kainulainen,Hendrik Linz
Physics , 2014, DOI: 10.1051/0004-6361/201423401
Abstract: Throughout the Milky Way, molecular clouds typically appear filamentary, and mounting evidence indicates that this morphology plays an important role in star formation. What is not known is to what extent the dense filaments most closely associated with star formation are connected to the surrounding diffuse clouds up to arbitrarily large scales. How are these cradles of star formation linked to the Milky Way's spiral structure? Using archival Galactic plane survey data, we have used multiple datasets in search of large-scale, velocity-coherent filaments in the Galactic plane. In this paper, we present our methods employed to identify coherent filamentary structures first in extinction and confirmed using Galactic Ring Survey data. We present a sample of seven Giant Molecular Filaments (GMFs) that have lengths of order $\sim$100 pc, total masses of 10$^4$ - 10$^5$ M$_{\odot}$, and exhibit velocity coherence over their full length. The GMFs we study appear to be inter-arm clouds and may be the Milky Way analogues to spurs observed in nearby spiral galaxies. We find that between 2 and 12% of the total mass (above $\sim$10$^{20}$ cm$^{-2}$) is "dense" (above 10$^{22}$ cm$^{-2}$), where filaments near spiral arms in the Galactic midplane tend to have higher dense gas mass fractions than those further from the arms.
Triggered/sequential star formation? A multi-phase ISM study around the prominent IRDC G18.93-0.03
J. Tackenberg,H. Beuther,R. Plume,T. Henning,J. Stil,M. Walmsley,F. Schuller,A. Schmiedeke
Physics , 2012, DOI: 10.1051/0004-6361/201220140
Abstract: G18.93-0.03 is a prominent dust complex within an 0.8deg long filament, with the molecular clump G18.93/m being IR dark from near IR wavelength up to 160mu. Spitzer composite images show an IR bubble spatially associated with G18.93. We use GRS 13CO and IRAM 30m H13CO+ data to disentangle the spatial structure of the region. From ATLASGAL submm data we calculate the gas mass, while we use the H13CO+ line width to estimate its virial mass. Using HERSCHEL data we produce temperature maps from fitting the SED. With the MAGPIS 20cm and SuperCOSMOS Halpha data we trace the ionized gas, and the VGPS HI survey provides information on the atomic hydrogen gas. We show that the bubble is spatially associated with G18.93, located at a kinematic near distance of 3.6kpc. With 280Msun, the most massive clump within G18.93 is G18.93/m. The virial analysis shows that it may be gravitationally bound and has neither Spitzer young stellar objects nor mid-IR point sources within. Fitting the SED reveals a temperature distribution that decreases towards its center, but heating from the ionizing source puts it above the general ISM temperature. We find that the bubble is filled by HII gas, ionized by an O8.5 star. Between the ionizing source and the IR dark clump G18.93/m we find a layered structure, from ionized to atomic to molecular hydrogen, revealing a PDR. Furthermore, we identify an additional velocity component within the bubble's 8mu emission rim at the edge of the infrared dark cloud and speculate that it might be shock induced by the expanding HII region. While the elevated temperature allows for the build-up of larger fragments, and the shock induced velocity component may lead to additional turbulent support, we do not find conclusive evidence that the massive clump G18.93/m is prone to collapse because of the expanding HII region.
The Mind’s Irreducible Structure  [PDF]
Mark Simes
Sociology Mind (SM) , 2012, DOI: 10.4236/sm.2012.23033
Abstract: The human mind is one of our most compelling subjects of scientific inquiry—and perhaps our most elusive. Despite impressive biological advances, neuroscience has yet to produce a logical and empirical analysis of the mind that exhibits universal, objective explanatory power of human mental phenomena on both an individual and species level. This article first explores the limitations of the current neuroscientific approach to the human mind and then argues for a reconceptualization of the relationship between human mental phenomena and the brain. Here I introduce a new interpretation of neuroscientific data and argue that this framework has the capacity to causally explain the link between social, psychological and biological levels of analysis.
Why Asynchronous Computer-Mediated Communication (ACMC) Is a Powerful Tool for Language Learning  [PDF]
Mark Brooke
Open Journal of Modern Linguistics (OJML) , 2012, DOI: 10.4236/ojml.2012.23016
Abstract: Tertiary institutions are increasingly using online virtual environments such as Blackboard to upload course content for students. However, there is still limited usage of the online blogging and discussion tools. This study describes the language used by tertiary students involved in blogging and discussions online. It also demonstrates learning processes observed through the interactions of participants over time. Findings suggest that this unique discourse mode is a potentially powerful tool for language learning.
Enhancing Pre-Service Teacher Training: The Construction and Application of a Model for Developing Teacher Reflective Practice Online  [PDF]
Mark Brooke
Open Journal of Modern Linguistics (OJML) , 2012, DOI: 10.4236/ojml.2012.24023
Abstract: Reflective practice is an essential component of pre-service teacher training programs. It facilitates the linking of theory and practice and empowers trainees to seek reasons behind their practices and their beliefs. These help novices to evolve as they witness their own teaching philosophies emerging. This research took place over 18 months and comprised 3 case studies of eight weeks with 3rd year ESOL trainees on their first intensive block practice in Hong Kong state schools. The research suggests that an online environment is an effective one in supporting and developing reflective practice during these periods. This was facilitated by asking trainees to apply an online model to scaffold reflections. These reflections were then posted and discussed by all case study members. They were also explored further using online moderator asynchronous Socratic dialogue to prompt further reflection. Findings demonstrate that a deep level of reflection is attainable in this context, albeit relatively rare, using the online medium.
A Critical Analysis of Selected Policy Making Decisions in the US and the UK with Regard to the Implementation of Information and Communication Technology (ICT) in National State Primary and Secondary School Education Systems  [PDF]
Mark Brooke
Open Journal of Modern Linguistics (OJML) , 2013, DOI: 10.4236/ojml.2013.31012
Abstract: Information and Communication Technology has played an important and pervasive role in modern business and everyday living over the last decade and more. The industry accounts for trillions of annual revenue. Yet, it has proved hard for a similar role for Information and Communication Technology (ICT) to emerge in education. In this paper, I will argue that policy regarding ICT use at national state levels in the UK and the US has striven to create, and continues to perpetuate, a system of education with technological divisions of labour, and marginalized innovative and communicative practical uses of technology for enhancing education in schools.
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