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91.
The fly Drosophila melanogaster can discriminate and remember visual landmarks. It analyses selected parts of its visual environment according to a small number of pattern parameters such as size, colour or contour orientation, and stores particular parameter values. Like humans, flies recognize patterns independently of the retinal position during acquisition of the pattern (translation invariance). Here we show that the central-most part of the fly brain, the fan-shaped body, contains parts of a network mediating visual pattern recognition. We have identified short-term memory traces of two pattern parameters--elevation in the panorama and contour orientation. These can be localized to two groups of neurons extending branches as parallel, horizontal strata in the fan-shaped body. The central location of this memory store is well suited to mediate translational invariance. 相似文献
92.
Goodridge HS Reyes CN Becker CA Katsumoto TR Ma J Wolf AJ Bose N Chan AS Magee AS Danielson ME Weiss A Vasilakos JP Underhill DM 《Nature》2011,472(7344):471-475
Innate immune cells must be able to distinguish between direct binding to microbes and detection of components shed from the surface of microbes located at a distance. Dectin-1 (also known as CLEC7A) is a pattern-recognition receptor expressed by myeloid phagocytes (macrophages, dendritic cells and neutrophils) that detects β-glucans in fungal cell walls and triggers direct cellular antimicrobial activity, including phagocytosis and production of reactive oxygen species (ROS). In contrast to inflammatory responses stimulated upon detection of soluble ligands by other pattern-recognition receptors, such as Toll-like receptors (TLRs), these responses are only useful when a cell comes into direct contact with a microbe and must not be spuriously activated by soluble stimuli. In this study we show that, despite its ability to bind both soluble and particulate β-glucan polymers, Dectin-1 signalling is only activated by particulate β-glucans, which cluster the receptor in synapse-like structures from which regulatory tyrosine phosphatases CD45 and CD148 (also known as PTPRC and PTPRJ, respectively) are excluded (Supplementary Fig. 1). The 'phagocytic synapse' now provides a model mechanism by which innate immune receptors can distinguish direct microbial contact from detection of microbes at a distance, thereby initiating direct cellular antimicrobial responses only when they are required. 相似文献
93.
Enhancing Organisational Innovation Capability Through Systemic Action Research: A Case of a Swiss SME in the Food Industry 总被引:2,自引:2,他引:0
Pierre-Yves Kocher Stephanie Kaudela-Baum Patricia Wolf 《Systemic Practice and Action Research》2011,24(1):17-44
This paper presents detailed insights into the nature of innovation dynamics of an SME operating in the food industry. Furthermore, the paper highlights how Action Research has changed and enhanced SME??s capability to innovate. Within the exploratory action research based case study described in this article, the researchers interacted closely with one company with regards to a newly launched innovation process over a time period of more than 18 months. The analysis contributes to the fields of action research and innovation research in three respects: First, it exemplifies how systemic action research as a method can be applied on the organisational level in the private sector. Second, it demonstrates how useful action research can be for fostering the innovativeness and creativity of a company. Lastly, the analysis illustrates the extensive time horizon of an action research project. 相似文献
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96.
H. U. Wolf 《Cellular and molecular life sciences : CMLS》1973,29(2):241-249
Zusammenfassung Es werden Puffersysteme für divalente Metallionen beschrieben, die im Bereich von etwa pH 6–10 gegenüber den herkömmlichen Metallpuffern eine bemerkenswert niedrige pH-Abhängigkeit der Metallionenkonzentration und der Pufferkapazität zeigen.Die Puffersysteme bestehen aus einem starken Komplexbildner (vorzugsweise einer Polyaminocarbonsäure) und zwei verschiedenen, divalenten Metallionen, die bezüglich der Bindung durch den Komplexbildner in Konkurrenz stehen. Dasjenige Metallion, dessen Konzentration gepuffert werden soll, wird als Primärion bezeichnet. Das zweite Ion, das Sekundärion genannt wird, soll vom Komplexbildner mindestens um den Faktor 10–100 schwacher gebunden werden.Die Gesamtkonzentration des Primärions ist geringer als diejenige des Komplexbildners, während die Summe der Gesamtkonzentrationen der beiden divalenten Metallionen höher ist als diejenige des Komplexbildners.Die Konzentration des freien Primärions kann in den beschriebenen Puffersystemen auf drei verschiedene Arten variiert werden: 1. durch Änderung der Gesamtkonzentration des Primärions, 2. durch Änderung der Gesamtkonzentration des Sekundärions, und 3. durch die Wahl eines passenden Komplexbildners mit entsprechenden Metallionen- und Protonendissoziationskonstanten.
Acknowledgments. The author wishes to thank MissU. Stechert for the design of the graphs. This work was supported by a grant of the Deutsche Forschungsgemeinschaft. 相似文献
Acknowledgments. The author wishes to thank MissU. Stechert for the design of the graphs. This work was supported by a grant of the Deutsche Forschungsgemeinschaft. 相似文献
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98.
Epstein--Barr virus-induced cell fusion 总被引:6,自引:0,他引:6
Serological and molecular biological studies have shown an association between Epstein--Barr virus (EBV) and nasopharyngeal carcinoma. Although it has been shown that the epithelioid tumour cells carry EBV genomes, they are apparently devoid of receptors for EBV (H.W., unpublished observations). Other have suggested that fusion of EBV carrying cells with epithelial cells may be the mode of entry of the virus into cells unable to absorb the virus and that this may be mediated by one of the known syncytium-forming viruses which inhabit the respiratory tract (for example, members of the paramyxovirus group). de Thé and colleagues suggested that intercellular bridges could be seen in NPC tumour material. We have developed a technique which permits the preparation of stable monolayers of viable human lymphoblastoid cell lines. Using this technique we have now demonstrated that EBV can induce fusion between EBV-superinfected lymphoblastoid cells and cells devoid of EBV receptors. 相似文献
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100.
Microbial legradation of bitumen 总被引:1,自引:0,他引:1
Summary Bitumen is commonly employed as a matrix for the long-term storage of low and intermediate level radioactive waste. As bitumen can be degraded by microbial activity, it is of great significance to determine the rates at which it may occur in nuclear waste repositories.Experiments have been carried out under optimal culture conditions using bitumen with a highly increased surface area. The potential of different microbial consortia to degrade bitumen has been examined. The investigations showed clearly that bitumen-degrading organisms are ubiquitous. In general the organisms formed biofilms on the accessible substrate surface area. Under oxic culture conditions a bitumen degradation rate of 20–50 g bitumen · m–2· y–1 leading to a CO2 liberation of 15–40 l was observed. Anoxic conditions yielded a 100 times smaller degradation rate of 0.2–0.6 g bitumen · m–2 · y–1 and a CO2 production of 0.15–0.45 l.Based on linear extrapolation the experimentally determined degradation rates would lead to a 25–70% deterioration of the bitumen matrix under oxic and 0.3–0.8% under anoxic conditions within 1000 years. 相似文献