University of Osnabru ck

Germany

University of Osnabru ck

Germany
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Lammers K.,University of Osnabrück | Abeln B.,University of Osnabrück | Husken M.,University of Osnabrück | Lehmacher C.,University of Osnabrück | And 4 more authors.
Journal of Experimental Biology | Year: 2017

Drosophila harbours a simple tubular heart that ensures haemolymph circulation within the body. The heart is built by a few different cell types, including cardiomyocytes that define the luminal heart channel and ostia cells that constitute openings in the heart wall allowing haemolymph to enter the heart chamber. Regulation of flow directionality within a tube, such as blood flow in arteries or insect haemolymph within the heart lumen, requires a dedicated gate, valve or flap-like structure that prevents backflow of fluids. In the Drosophila heart, intracardiac valves provide this directionality of haemolymph streaming, with one valve being present in larvae and three valves in the adult fly. Each valve is built by two specialised cardiomyocytes that exhibit a unique histology.We found that the capacity to open and close the heart lumen relies on a unique myofibrillar setting as well as on the presence of large membranous vesicles. These vesicles are of endocytic origin and probably represent unique organelles of valve cells. Moreover, we characterised the working mode of the cells in real time. Valve cells exhibit a highly flexible shape and, during each heartbeat, oscillating shape changes result in closing and opening of the heart channel. Finally, we identified a set of novel valve cell markers useful for future in-depth analyses of cell differentiation in wild-type and mutant animals. © 2017. Published by The Company of Biologists Ltd.


Ko ster M.,University of Osnabru ck | Friese U.,University of Hamburg | Scho ne B.,University of Osnabru ck | Trujillo-Barreto N.,Cuban Neuroscience Center | Gruber T.,University of Osnabru ck
Brain Research | Year: 2014

Recent findings indicate that phase-amplitude coupling between neuronal oscillations in the theta- (3-6. Hz) and the gamma-band (30-100. Hz) plays a functional role in memory processes. Here, using electroencephalography, we provide further evidence for coupling between prefrontal theta and parietal gamma during successful memory retrieval in the human brain. In a pictorial recognition task, the coupling between prefrontal theta phase and parietal gamma amplitude was quantified using the modulation index, 100-1500. ms after stimulus onset. Results show an increased coupling for remembered, as opposed to forgotten and new stimuli (. i.e. a "recognition effect" and an "old/new effect"). Phase-amplitude coupling between the prefrontal theta phase and posterior gamma amplitudes is hypothesized to reflect long range communication between prefrontal control processes and the activation of posterior object representations accompanying mnemonic processing. © 2014.


Borchard F.,University of Mu nster | Buchholz S.,TU Berlin | Helbing F.,University of Mu nster | Fartmann T.,University of Mu nster | Fartmann T.,University of Osnabru ck
Biological Conservation | Year: 2014

Semi-natural habitats such as heathland ecosystems are important for the conservation of biodiversity. Due to land use changes, these valuable ecosystems have become highly threatened. Nowadays, their management and restoration is of special relevance for nature conservation. In this study, we used carabid beetles and spiders as bioindicators to evaluate the success of montane heathland restoration on former spruce forests. We compared three different treatments: (i) montane heathlands (MONHEATH), (ii) restoration (RESSITE) and (iii) control (CONTROL) sites. Four to five years after conducting the restoration measures, all environmental variables, except soil moisture, significantly differed between MONHEATH on one hand and RESSITE and CONTROL on the other. MONHEATH was characterised by a high cover of dwarf shrubs; in contrast, RESSITE/CONTROL had a vegetation rich in herbs/grasses with some bare ground. Both carabid beetle and spider assemblage composition clearly reflected these differences in environmental conditions. Alpha-diversity (Simpson diversity, evenness) and niche positions were, however, only significantly different for spiders. Diversity as well as spider indicator values for shade and moisture were higher for MONHEATH. Due to the cool and wet montane climate and the dense dwarf-shrub stands the carabid beetle and spider species characteristic of MONHEATH are typical woodland species. Four to five years after restoration, RESSITE and CONTROL still represent early successional stages with a low cover of the Ericaceae target dwarf shrubs (Calluna vulgaris, Vaccinium myrtillus and Vaccinium vitis-idaea), but are already home to some typical heathland carabid beetle and spider species that are missing in MONHEATH. © 2014 Elsevier Ltd.

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