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41.
Tobias Ruck Stefanie Bock Steffen Pfeuffer Christina B.Schroeter Derya Cengiz Paul Marciniak Maren Lindner Alexander Herrmann Marie Liebmann Stjepana Kovac Lukas Gola Leoni Rolfes Marc Pawlitzki Nils Opel Tim Hahn Udo Dannlowski Thomas Pap Felix Luessi Julian A.Schreiber Bernhard Wünsch Tanja Kuhlmann Guiscard Seebohm Bjrn Tackenberg Patricia Seja Frank Dring Erhard Wischmeyer Achmet Imam Chasan Johannes Roth Luisa Klotz Gerd Meyer zu Hrste Heinz Wiendl Tobias Marschall Stefan Floess Jochen Huehn Thomas Budde Tobias Bopp Stefan Bittner Sven G.Meuth 《Cell research》2022,32(1):72-88
It remains largely unclear how thymocytes translate relative differences in T cell receptor (TCR) signal strength into distinct developmental programs that driv... 相似文献
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Werner Baumgartner Friederike Saxe Agnes Weth David Hajas Darwin Sigumonrong Jens Emmerlich Martin Singheiser Wolfgang Bhme Jochen M. Schneider 《仿生工程学报(英文版)》2007,4(1)
The sandfish is a lizard having the remarkable ability to move in desert sand in a swimming-like fashion. The most out-standing adaptations to this mode of life are the low friction behaviour and the extensive abrasion resistance of the sandfish skin against sand, outperforming even steel. We investigated the topography, the composition and the mechanical properties of sandfish scales. These consist of glycosylated keratins with high amount of sulphur but no hard inorganic material, such as silicates or lime. Remarkably, atomic force microscopy shows an almost complete absence of attractive forces between the scale surface and a silicon tip, suggesting that this is responsible for the unusual tribological properties. The unusual glycosylation of the keratins was found to be absolutely necessary for the described phenomenon. The scales were dissolved and reconstituted on a polymer surface resulting in properties similar to the original scale. Thus, we provide a pathway towards exploitation of the reconstituted scale material for future engineering applications. 相似文献
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Differentiation of isolated wheat zygotes into embryos and normal plants 总被引:19,自引:0,他引:19
Efficient and reproducible embryo development has been obtained from fertilized wheat (Triticum aestivum L.) egg cells isolated 3–6 h after hand-pollination of emasculated spikes. It is possible to routinely isolate viable zygotes
from about 75% of the excised ovaries from cultivars of both winter and spring types. Co-culture with barley microspores which
had been stimulated to sporophytic development resulted in embryonic development of the cultivated wheat zygotes. Within 23 h
of pollination; the zygotes underwent their first cell division. They proceeded to develop into club-shaped embryos, most
of which turned subsequently to dorsiventral differentiation. The morphological patterns of in-vitro-grown embryos were in
accordance with those of normal zygotic embryos growing in planta. The formation of twin or multiple embryos originating from
a single zygote was dependent on genotype and exogeneously supplied auxin. Upon transfer onto a suitable solidified medium,
zygote-derived embryos usually germinated and developed into plants. After optimizing the feeder system, the nutrient medium
and the concentration of 2,4-dichloro phenoxyacetic acid (2,4-D), more than 80 and 90% of the zygotes eventually developed
into plants in genotypes Florida and Veery #5, respectively. All regenerated plants were morphologically normal and fertile.
The in-vitro development from isolated zygotes of a higher-plant species into typically patterned zygotic embryos is shown
here for the first time. Since the entire process, including early zygotic development, is now freely accessible to observation
and micromanipulation, the method presented opens up new approaches in fundamental as well as applied fields of reproductive
biology.
Received: 4 September 1997 / Accepted: 28 November 1997 相似文献
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Soil-air exchange of nitric oxide: An overview of processes, environmental factors, and modeling studies 总被引:8,自引:0,他引:8
Terrestrial ecosystems with their main elements soil and plants may act, in principle, as both source and sink for atmospheric nitric oxide (NO). The net exchange between ecosystems and the atmosphere, however, is globally dominated by biogenic emissions of NO from soils. Consequently the soil–air exchange of NO is the focus of the following overview. Particular emphasis is placed on the major processes that are responsible for NO production in soils (nitrification, denitrification) and their regulation by environmental factors (nitrogen availability, soil water content, soil temperature, ambient NO concentration). It is shown that interactions of these factors are a major reason for the broad range that exists in published data on NO fluxes. This variability makes it difficult to predict the magnitude of NO fluxes on relevant spatial and temporal scales. To overcome the problem various generalization procedures for scaling up in space and time have been developed, and the potential and limitations of the different approaches is discussed. 相似文献
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Dynamics of the yeast transcriptome during wine fermentation reveals a novel fermentation stress response 总被引:3,自引:0,他引:3
Marks VD Ho Sui SJ Erasmus D van der Merwe GK Brumm J Wasserman WW Bryan J van Vuuren HJ 《FEMS yeast research》2008,8(1):35-52
In this study, genome-wide expression analyses were used to study the response of Saccharomyces cerevisiae to stress throughout a 15-day wine fermentation. Forty per cent of the yeast genome significantly changed expression levels to mediate long-term adaptation to fermenting grape must. Among the genes that changed expression levels, a group of 223 genes was identified, which was designated as fermentation stress response (FSR) genes that were dramatically induced at various points during fermentation. FSR genes sustain high levels of induction up to the final time point and exhibited changes in expression levels ranging from four- to 80-fold. The FSR is novel; 62% of the genes involved have not been implicated in global stress responses and 28% of the FSR genes have no functional annotation. Genes involved in respiratory metabolism and gluconeogenesis were expressed during fermentation despite the presence of high concentrations of glucose. Ethanol, rather than nutrient depletion, seems to be responsible for entry of yeast cells into the stationary phase. 相似文献
48.
Biodiversity can provide insurance against environmental change, but only if species differ in their response to environmental conditions (response diversity). Wild bees provide pollination services to wild and crop plants, and response diversity might insure this function against changing climate. To experimentally test the hypothesis that bee species differ in their response to increasing winter temperature, we stored cocoons of nine bee species at different temperatures during the winter (1.5–9.5 °C). Bee species differed significantly in their responses (weight loss, weight at emergence and emergence date). The developmental stage during the winter explained some of these differences. Bee species overwintering as adults generally showed decreased weight and earlier emergence with increasing temperature, whereas bee species overwintering in pre-imaginal stages showed weaker or even opposite responses. This means that winter warming will likely affect some bee species negatively by increasing energy expenditure, while others are less sensitive presumably due to different physiology. Likewise, species phenologies will respond differently to winter warming, potentially affecting plant–pollinator interactions. Responses are not independent of current flight periods: bees active in spring will likely show the strongest phenological advances. Taken together, wild bee diversity provides response diversity to climate change, which may be the basis for an insurance effect. 相似文献
49.
Hans -Ortwin Nalbach Jochen Zeil Luise Forzin 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1989,165(5):643-649
1. | We recorded compensatory eye stalk movements in response to pitch and roll stimulation of the visual, statocyst, and leg-proprioceptive systems in different species of crabs (Carcinus maenas, Heloecius cordiformis, Pachygrapsus marmoratus) (Fig. 2). |
2. | The relative contribution of visual, statocyst and leg-proprioceptive inputs to eye stabilization in space varies greatly among different species (Fig. 3). |
3. | We suggest that for stabilizing the eyes in space, the contribution of various sensory inputs in different species of crabs correspond to the availability of cues in their habitat. Semiterrestrial crabs living in a habitat with well defined and predictable visual geometry stabilize their eye stalks mainly by visual cues. Crabs living on solid substrate make strong use of leg proprioceptive input. Swimming crabs, and other predominantly aquatic crabs, rely mainly on their statocysts. |
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