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Daw-Yang Hwang Stefan Kohl Xueping Fan Asaf Vivante Stefanie Chan Gabriel C. Dworschak Julian Schulz Albertien M. van Eerde Alina C. Hilger Heon Yung Gee Tracie Pennimpede Bernhard G. Herrmann Glenn van de Hoek Kirsten Y. Renkema Christoph Schell Tobias B. Huber Heiko M. Reutter Neveen A. Soliman Natasa Stajic Radovan Bogdanovic Elijah O. Kehinde Richard P. Lifton Velibor Tasic Weining Lu Friedhelm Hildebrandt 《Human genetics》2015,134(8):905-916
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Miilena M. Awad Amy E. Bryant Dennis L. Stevens Julian I. Rood 《Molecular microbiology》1995,15(2):191-202
The pathogenesis of clostridial myonecrosis, or gas gangrene, involves the growth of the anaerobic bacterium Clostridium perfringens in the infected tissues and the elaboration of numerous extracellular toxins and enzymes. The precise role of each of these toxins in tissue invasion and necrosis has not been determined. To enable genetic approaches to be used to study C. perfringens pathogenesis we developed an allelic exchange method which involved the transformation of C. perfringens cells with a suicide plasmid carrying a gene insertionally inactivated with an erythromycin-resistance determinant. The frequency with which double reciprocal crossover events were observed was increased to a workable level by increasing the amount of homologous DNA located on either side of the inactivated gene. Allelic exchange was used to isolate mutations in the‘chromosomal pfoA gene, which encodes an oxygen-labile haemolysin known as Θ-toxin or perfringolysin O. and in the chromosomal pic gene, which encodes the α-toxin or phospholipase C. The resultant mutants failed to produce detectable Θ-toxin or α-toxin activity, respectively, and could be complemented by recombinant plasmids that carried the respective wild-type genes. The resultant strains were virulence tested in a mouse myonecrosis model. The results showed that the pic mutants had demonstrably reduced virulence and therefore provided definitive genetic evidence for the essential role of α-toxin in gas gangrene or clostridial myonecrosis. 相似文献
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In commerce, Asiatic lilies are picked in bud, each stem holdingseveral buds. We found flower opening was rapid, taking lessthan 4 h both on the stem and for excised buds. Opening wasalso strongly synchronous. For a 12 h day-night cycle, openingbegan late in the dark period, reaching a mid-point after 11h of darkness. This was equally true of buds that were excisedwhen nearly ready to open, and those with 34 d of developmentto complete. Reversing day and night reversed the time of opening,and red light was as effective as white light in providing dayconditions. A 15 min light break during the night did not affectthe opening. Lengthening the night (8, 12, 16 h) and shorteningthe day delayed opening from 9, to 11, to 13 h after the startof darkness, respectively. In continuous light and continuousdark, synchronicity was lost. If opening flowers were held inextended darkness, two phases of opening could be discriminated.In a dark phase, petals opened to approx. 40°,and anthers remained intact. When such flowers were returnedto light, there was a light phase, where petalsopened further, became more pigmented and began to recurve,and the anthers dehisced, these events taking only 23h. The net result was that flowers became fully open and anthersdehisced approx. 2 h after dawn, regardless of daylength. Copyright2000 Annals of Botany Company Asiatic lily, Lilium hybrid, flower opening, timing, endogenous rhythm, synchronicity 相似文献
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Applications——Influence of Biology on Engineering 总被引:1,自引:0,他引:1
Julian F. V. Vincent 《仿生工程学报(英文版)》2006,3(3):161-177
Examples are presented showing the way in which biological systems produce a range of functions which can be implemented in engineering, such as feedback-control of stiffness (muscles and nervous system), the design of fault-free structures (trees) and damage-tolerant materials (wood) and high performance insulation (penguin feathers) and shock absorbers (hedgehog spines). 相似文献
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