共查询到20条相似文献,搜索用时 15 毫秒
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Chromosomal evolution: inversions: the chicken or the egg? 总被引:2,自引:0,他引:2
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Phytochemicals: the good, the bad and the ugly? 总被引:2,自引:0,他引:2
Phytochemicals are constitutive metabolites that enable plants to overcome temporary or continuous threats integral to their environment, while also controlling essential functions of growth and reproduction. All of these roles are generally advantageous to the producing organisms but the inherent biological activity of such constituents often causes dramatic adverse consequences in other organisms that may be exposed to them. Nevertheless, such effects may be the essential indicator of desirable properties, such as therapeutic potential, especially when the mechanism of bioactivity can be delineated. Careful observation of cause and effect, followed by a coordinated approach to identify the responsible entities, has proved extremely fruitful in discovering roles for phytochemical constituents. The process is illustrated by selected examples of plants poisonous to animals and include the steroidal alkaloid toxin of Veratrum californicum (Western false hellebore), piperidine alkaloids of Lupinus species (lupines), and polyhydroxy indolizidine, pyrrolizidine and nortropane alkaloids of Astragalus and Oxytropis species (locoweeds), Castanospermum australe (Moreton Bay chestnut) and Ipomoea species (morning glories). 相似文献
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Malissen B 《Médecine sciences : M/S》2007,23(2):115-116
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Soto C 《Trends in biochemical sciences》2011,36(3):151-158
Forty-three years have passed since it was first proposed that a protein could be the sole component of the infectious agent responsible for the enigmatic prion diseases. Many discoveries have strongly supported the prion hypothesis, but only recently has this once heretical hypothesis been widely accepted by the scientific community. In the past 3 years, researchers have achieved the 'Holy Grail' demonstration that infectious material can be generated in vitro using completely defined components. These breakthroughs have proven that a misfolded protein is the active component of the infectious agent, and that propagation of the disease and its unique features depend on the self-replication of the infectious folding of the prion protein. In spite of these important discoveries, it remains unclear whether another molecule besides the misfolded prion protein might be an essential element of the infectious agent. Future research promises to reveal many more intriguing features about the rogue prions. 相似文献
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R Cooke 《Current biology : CB》1999,9(20):R773-R775
Previous crystal structures of the myosin head have shown two different conformations, postulated to be the beginning and the end of the actomyosin power stroke. A new crystal structure reveals a dramatically different conformation; but how does this conformation fit into the force-generating cycle of actomyosin interactions? 相似文献
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Izquierdo-Useros N Puertas MC Borràs FE Blanco J Martinez-Picado J 《Cellular microbiology》2011,13(1):10-17
Retroviruses appropriate pre‐existing cellular machineries to propagate. In the last decade, impressive similarities have been observed in the generation and dissemination in the host cells of retroviruses and small cellular vesicles known as exosomes. These cellular vesicles are thought to facilitate intercellular communication processes and mediate immune functions. However, their link to the retroviral life cycle has given rise to distinct hypotheses and puzzling dilemmas. Are exosomes the antecessors of retroviruses or do retroviruses merely exploit the same cellular machinery designated for exosome biosynthesis? Here, we address these fascinating evolutionary questions by reviewing recent discoveries and analysing the controversies surrounding them. 相似文献
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A silver-staining technique specific for demonstrating nucleolus organizer regions (NOR) showed that the achromatic stalks of the 10 acrocentric autosomes of the human complement represent the NORs. Some variability in number of stained stalks is observed from cell-to-cell and from individual-to-individual. The silver-stained masses may extend beyond the stalks and cover the satellites, especially in chromosomes with short stalks or minute satellites. 相似文献
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A key problem in developmental biology is understanding the origin of morphological innovations. Comparative studies in plants with different leaf morphologies indicate that the developmental pathway defined by KNOTTED1-type homeodomain proteins could be involved in generating different leaf forms. The differential expression of regulatory proteins has emerged as an important factor in driving morphological innovations in the plant kingdom--an idea that is well supported by quantitative trait locus analyses. 相似文献