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101.
Richter P Börnig A Streb C Ntefidou M Lebert M Häder DP 《Journal of plant physiology》2003,160(6):651-656
The unicellular freshwater flagellate Euglena gracilis regulates its position in the water column by means of phototactic and gravitactic behavior. Recent experiments have revealed that the cells switch between negative and positive gravitaxis depending upon environmental stimuli such as solar radiation. In this study, the effect of increased salinity on gravitaxis in Euglena gracilis was investigated. In some experiments it was found that salt concentrations up to 5 gL-1 (in some experiments 10 gL-1) increased the motility, velocity and precision of negative gravitactic orientation. Higher salt concentrations decreased all these parameters. At concentrations of about 15 gL-1, cells which did not become immobile, switched from negative to positive gravitaxis. Positive gravitaxis persisted for several hours or even days when the cells were transferred back to standard culture medium. Most of the cells in cultures exposed to salt concentrations above 20 gL-1 lost their motility (partial formation of palmella stages) but recovered when transferred back to standard medium or de-ionised water. Post recovery, the cells showed pronounced positive gravitaxis. Additional investigations on the pigmentation, revealed that the cells showed a complete loss of a carotenoid shoulder in the spectrum, which reappeared when the cells were brought back to standard medium. 相似文献
102.
103.
Influence of morphology and rheology on the production characteristics of the basidiomycete Cyathus striatus 总被引:3,自引:0,他引:3
The influence of the pellet morphology of the basidiomycete Cyathus striatus on the production of the antibiotics striatals A, B, and C was investigated. The main operating parameters in fermenters of different sizes were the tip speed and the volumetric power input. Different methods were developed for quantification of morphological characteristics. The apparent viscosity of the suspension was measured with a cylinder rheometer. Sediment density was measured with a sedimentation apparatus. Particle size distributions were recorded with an image analysis system. By means of the presented measuring methods, morphological characteristics could be determined and enabled an early assessment of the fermentation course and the antibiotics production. During the exponential growth phase of the fungus the relative sediment height correlated with the biomass concentration. The pellet morphology at this stage influenced the later production of striatals. The yield of the striatals was markedly influenced by pellet size and sediment density. Since these morphological characteristics determine the rheological properties of the culture the measurement of the apparent viscosity of the culture in the production phase allowed predictions of the production yield. 相似文献
104.
Christian van den Bos Anke Rammes Thomas Vogl Raymond Boynton Joseph Zaia Clemens Sorg Johannes Roth 《Protein expression and purification》1998,13(3):313-318
A method is described for purification of P6, MRP8, and MRP14, three calcium-binding proteins assigned to the S100 protein family. The purification procedure included preparation of human granulocytes, ammonium sulfate precipitation, and anion-exchange chromatography and resulted in the copurification of P6, MRP8, and MRP14. Individual proteins were separated by either preparative isoelectric focusing or preparative SDS–PAGE. The procedure was carried out in the course of 4 days and yielded several milligrams of essentially pure P6, MRP8, and MRP14 in either native or denatured form. 相似文献
105.
Bjoern von Einem Anke Wahler Tobias Schips Alberto Serrano-Pozo Christian Proepper Tobias M. Boeckers Angelika Rueck Thomas Wirth Bradley T. Hyman Karin M. Danzer Dietmar R. Thal Christine A. F. von Arnim 《PloS one》2015,10(6)
Proteolytic processing of amyloid-β precursor protein (APP) by beta-site APP cleaving enzyme 1 (BACE1) is the initial step in the production of amyloid beta (Aβ), which accumulates in senile plaques in Alzheimer’s disease (AD). Essential for this cleavage is the transport and sorting of both proteins through endosomal/Golgi compartments. Golgi-localized γ-ear-containing ARF-binding (GGA) proteins have striking cargo-sorting functions in these pathways. Recently, GGA1 and GGA3 were shown to interact with BACE1, to be expressed in neurons, and to be decreased in AD brain, whereas little is known about GGA2. Since GGA1 impacts Aβ generation by confining APP to the Golgi and perinuclear compartments, we tested whether all GGAs modulate BACE1 and APP transport and processing. We observed decreased levels of secreted APP alpha (sAPPα), sAPPβ, and Aβ upon GGA overexpression, which could be reverted by knockdown. GGA-BACE1 co-immunoprecipitation was impaired upon GGA-GAE but not VHS domain deletion. Autoinhibition of the GGA1-VHS domain was irrelevant for BACE1 interaction. Our data suggest that all three GGAs affect APP processing via the GGA-GAE domain. 相似文献
106.
Matthias Hammon Susan Grossmann Peter Linz Christoph Kopp Anke Dahlmann Christoph Garlichs Rolf Janka Alexander Cavallaro Friedrich C. Luft Michael Uder Jens Titze 《PloS one》2015,10(10)
Objective
Na+ can be stored in muscle and skin without commensurate water accumulation. The aim of this study was to assess Na+ and H2O in muscle and skin with MRI in acute heart failure patients before and after diuretic treatment and in a healthy cohort.Methods
Nine patients (mean age 78 years; range 58–87) and nine age and gender-matched controls were studied. They underwent 23Na/1H-MRI at the calf with a custom-made knee coil. Patients were studied before and after diuretic therapy. 23Na-MRI gray-scale measurements of Na+-phantoms served to quantify Na+-concentrations. A fat-suppressed inversion recovery sequence was used to quantify H2O content.Results
Plasma Na+-levels did not change during therapy. Mean Na+-concentrations in muscle and skin decreased after furosemide therapy (before therapy: 30.7±6.4 and 43.5±14.5 mmol/L; after therapy: 24.2±6.1 and 32.2±12.0 mmol/L; p˂0.05 and p˂0.01). Water content measurements did not differ significantly before and after furosemide therapy in muscle (p = 0.17) and only tended to be reduced in skin (p = 0.06). Na+-concentrations in calf muscle and skin of patients before and after diuretic therapy were significantly higher than in healthy subjects (18.3±2.5 and 21.1±2.3 mmol/L).Conclusions
23Na-MRI shows accumulation of Na+ in muscle and skin in patients with acute heart failure. Diuretic treatment can mobilize this Na+-deposition; however, contrary to expectations, water and Na+-mobilization are poorly correlated. 相似文献107.
Spatial and ecological population genetic structures within two island‐endemic Aeonium species of different niche width 下载免费PDF全文
David E. V. Harter Mike Thiv Alfons Weig Anke Jentsch Carl Beierkuhnlein 《Ecology and evolution》2015,5(19):4327-4344
The Crassulacean genus Aeonium is a well‐known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra‐island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island‐endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species. 相似文献
108.
The domestic dog may be the most morphologically diverse terrestrial mammalian species known to man; pedigree dogs are artificially selected for extreme aesthetics dictated by formal Breed Standards, and breed-related disorders linked to conformation are ubiquitous and diverse. Brachycephaly–foreshortening of the facial skeleton–is a discrete mutation that has been selected for in many popular dog breeds e.g. the Bulldog, Pug, and French Bulldog. A chronic, debilitating respiratory syndrome, whereby soft tissue blocks the airways, predominantly affects dogs with this conformation, and thus is labelled Brachycephalic Obstructive Airway Syndrome (BOAS). Despite the name of the syndrome, scientific evidence quantitatively linking brachycephaly with BOAS is lacking, but it could aid efforts to select for healthier conformations. Here we show, in (1) an exploratory study of 700 dogs of diverse breeds and conformations, and (2) a confirmatory study of 154 brachycephalic dogs, that BOAS risk increases sharply in a non-linear manner as relative muzzle length shortens. BOAS only occurred in dogs whose muzzles comprised less than half their cranial lengths. Thicker neck girths also increased BOAS risk in both populations: a risk factor for human sleep apnoea and not previously realised in dogs; and obesity was found to further increase BOAS risk. This study provides evidence that breeding for brachycephaly leads to an increased risk of BOAS in dogs, with risk increasing as the morphology becomes more exaggerated. As such, dog breeders and buyers should be aware of this risk when selecting dogs, and breeding organisations should actively discourage exaggeration of this high-risk conformation in breed standards and the show ring. 相似文献
109.
Michael J. Lawes Diana O. Fisher Chris N. Johnson Simon P. Blomberg Anke S. K. Frank Susanne A. Fritz Hamish McCallum Jeremy VanDerWal Brett N. Abbott Sarah Legge Mike Letnic Colette R. Thomas Nikki Thurgate Alaric Fisher Iain J. Gordon Alex Kutt 《PloS one》2015,10(6)
Australia has experienced dramatic declines and extinctions of its native rodent species over the last 200 years, particularly in southern Australia. In the tropical savanna of northern Australia significant declines have occurred only in recent decades. The later onset of these declines suggests that the causes may differ from earlier declines in the south. We examine potential regional effects (northern versus southern Australia) on biological and ecological correlates of range decline in Australian rodents. We demonstrate that rodent declines have been greater in the south than in the tropical north, are strongly influenced by phylogeny, and are consistently greater for species inhabiting relatively open or sparsely vegetated habitat. Unlike in marsupials, where some species have much larger body size than rodents, body mass was not an important predictor of decline in rodents. All Australian rodent species are within the prey-size range of cats (throughout the continent) and red foxes (in the south). Contrary to the hypothesis that mammal declines are related directly to ecosystem productivity (annual rainfall), our results are consistent with the hypothesis that disturbances such as fire and grazing, which occur in non-rainforest habitats and remove cover used by rodents for shelter, nesting and foraging, increase predation risk. We agree with calls to introduce conservation management that limits the size and intensity of fires, increases fire patchiness and reduces grazing impacts at ecological scales appropriate for rodents. Controlling feral predators, even creating predator-free reserves in relatively sparsely-vegetated habitats, is urgently required to ensure the survival of rodent species, particularly in northern Australia where declines are not yet as severe as those in the south. 相似文献
110.
Anke Huss Manon van Eijsden Monica Guxens Johan Beekhuizen Rob van Strien Hans Kromhout Tania Vrijkotte Roel Vermeulen 《PloS one》2015,10(10)