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Myosins in melanocytes: to move or not to move? 总被引:2,自引:0,他引:2
Coudrier E 《Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society》2007,20(3):153-160
The actin network has been implicated in the intracellular transport and positioning of the melanosomes, organelles that are specialized in the biosynthesis and the storage of melanin. It contributes also to molecular mechanisms that underlie the intracellular membrane dynamics and thereby can control the biogenesis of melanosomes. Two mechanisms for actin-based movements have been identified: one is dependent on the motors associated to actin namely the myosins; the other is dependent on actin polymerization. This review will focus on to the role of the actin cytoskeleton and myosins in the transport and in the biogenesis of melanosomes. Myosins involved in membrane traffic are largely seen as transporters of organelles or membrane vesicles containing cargos along the actin networks. Yet increasing evidence suggests that some of the myosins contribute to the dynamics of internal membrane by using other mechanisms. The role of the myosins and the different molecular mechanisms by which they contribute or may contribute to the distribution, the movement and the biogenesis of the melanosomes in epidermal melanocytes and retinal pigmented epithelial (RPE) cells will be discussed. 相似文献
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Semaphorins were discovered 11 years ago as molecular cues for axon guidance that are conserved from invertebrates to humans. More than 20 semaphorin genes have been identified in mammals and their protein products are now known to be involved in a range of processes from the guidance of cell migration to the regulation of the immune response, angiogenesis and cancer. Plexins, either alone or in association with neuropilins, constitute high-affinity semaphorin receptors. However, other transmembrane molecules have been implicated in semaphorin receptor complexes, and interactions between plexins and a range of intracellular effectors have been reported. These data indicate that semaphorins might be able to elicit responses through more than one signalling pathway. Interestingly, according to recent findings, the semaphorin-dependent control of cell migration crucially involves integrin-based adhesive structures through which polarized cell-membrane protrusion is coupled to cytoskeletal dynamics. This review focuses on the mechanisms whereby semaphorins are thought to regulate cell migration. 相似文献
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There has been a recent trend towards the miniaturization of analytical tools, but what are the advantages of microfluidic devices and when is their use appropriate? Recent advances in the field of micro-analytical systems can be classified according to instrument performance (which refers here to the desired property of the analytical tool of interest) and two important features specifically related to miniaturisation, namely reduction of the sample volume and the time-to-result. Here we discuss the contribution of these different parameters and aim to highlight the factors of choice in the development and use of microfluidic devices dedicated to protein analysis. 相似文献
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We recently found that nuclei take different intracellular positions depending upon dark and light conditions in Arabidopsis thaliana leaf cells. Under dark conditions, nuclei in both epidermal and mesophyll cells are distributed baso-centrally within the cell (dark position). Under light conditions, in contrast, nuclei are distributed along the anticlinal walls (light position). Nuclear repositioning from the dark to light positions is induced specifically by blue light at >50 µmol m−2 s−1 in a reversible manner. Using analysis of mutant plants, it was demonstrated that the response is mediated by the blue-light photoreceptor phototropin2. Intriguingly, phototropin2 also seems to play an important role in the proper positioning of nuclei and chloroplasts under dark conditions. Light-dependent nuclear positioning is one of the organelle movements regulated by phototropin2. However, the mechanisms of organelle motility, physiological significance, and generality of the phenomenon are poorly understood. In this addendum, we discussed how and why nuclei move depending on light, together with future perspectives.Key words: actin, Arabidopsis, blue light, cytoskeleton, nuclear positioning, nucleus, phototropin 相似文献
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Ruggiero P Peppoloni S Rappuoli R Del Giudice G 《Microbes and infection / Institut Pasteur》2003,5(8):749-756
Several lines of evidence from experimental animal models of infection have clearly demonstrated the feasibility of a prophylactic and therapeutic vaccine against Helicobacter pylori. However, comparatively few clinical studies have been carried out to evaluate whether the positive results obtained in animals can be reproduced in humans. The preliminary results obtained with single component, mucosally delivered vaccines have shown very limited results thus far. Very good immunogenicity and safety profiles are now being obtained with parenterally delivered, aluminium hydroxide-adjuvanted multicomponent candidate vaccines. For sure, better vaccine formulations, better antigen preparation(s), better adjuvants, and better delivery systems have to be designed and tested for safety and immunogenicity. These studies are also needed for deciphering those aspects of the effector immune responses that correlate with protection against H. pylori infection and disease. 相似文献
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Tracy X. Karner 《Ethnic and racial studies》2013,36(2):152-169
Sociologists often dismiss the emergence of unique nationalist identities as reflections of changing structural elements, namely the political and economic. In this article I view nationalism as a socially created and sustained ideological discourse. From this orientation, the importance of attending to cultural or symbolic constructions within nationalist movements becomes more pronounced. Thompson's (1987) re‐orien‐tational conceptions of ideology are used as an interpretative frame to analyse the construction of nineteenth‐century Finnish nationalism. Through this theoretical focus on language, the Kalevala, a book of Finnish folk poems, can be seen as a socio‐historical phenomenon amidst human conflict. This collection of poems provided the necessary discourse used to disrupt the previous Swedish cultural and emergent Russian political dominance. Symbolizing the invented culture, the Kalevala served as the basis for popular Finnishness, as well as politically mobilizing critical ideological assertions. The creation, transmission, and contestation of social meaning, through the use of language and material culture, specifically embodied in the Kalevala, is traced throughout the Finnish struggle for independence. 相似文献
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The octopus is amazingly flexible and shows exceptional control and coordination in all its movements. It seems remarkable to us skeletal creatures that the octopus achieves all this without a single bone. 相似文献
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M.M. Wachowski M. Mansour C. Lee A. Ackenhausen S. Spiering J. Fanghnel C. Dumont D. Kubein-Meesenburg H. Ngerl 《Journal of biomechanics》2009,42(14):2286-2293
PurposeTo study and clarify the kinematics of spinal segments following cyclic torques causing axial rotation (Tz (t)), lateral-flexion (Tx (t)), flexion/extension (Ty (t)).MethodsA 6D--Measurement of location, alignment, and migration of the instantaneous helical axis (IHA) as a function of rotational angle in cervical, thoracic, and lumbar segments subjected to axially directed preloads.ResultsIHA retained an almost constant alignment, but migrated along distinct centrodes.Thoracic segmentsIHA was almost parallel to Tz (t), Tx (t), or Ty (t), stationary for Tx (t) or Ty (t), and migrating for Tz (t) along dorsally opened bows. IHA locations hardly depended on the position or size of axial preload.Lumbar segmentsIHA was also almost parallel to Tz (t), Tx (t), or Ty (t). In axial rotation IHA-migration along wide, ventrally or dorsally bent bows depending on segmental flexional/extensional status. Distances covered: 20–60 mm. In lateral-flexion: IHA-migration to the left/right joint and vice versa. In flexion/extension IHA-migration from the facets to the centre of the disc.Cervical segmentsIn flexion/flexion IHA was almost stationary for and parallel to Ty (t). In axial rotation or lateral-flexion IHA intersected Tz (t)/Tx (t) under approximately ?30°/+30°.ConclusionsGenerally joints alternate in guidance. Lumbar segments: in axial rotation and lateral-flexion parametrical control of IHA-position and IHA-migration by axial preload position. Cervical segments: kinematical coupling between axial rotation and lateral-flexion.The IHA-migration guided by the joints should be taken into account in the design of non-fusion implants. FE-calculations of spinal mechanics and kinematics should be based on detailed data of curvature morphology of the articulating surfaces of the joint facets. 相似文献
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The movement of cells along surfaces is a complex phenomenon that consists of several interrelated processes, including cell-substratum adhesion, and extension and retraction of the cell edge, in which the actin cytoskeleton plays a crucial role. The past decade has seen increasingly detailed molecular-based investigations into cell motility, but it is still not known how molecular events are integrated to give cell movement. Molecular studies are now beginning to be linked to a more global concept of how whole cells move, and this combined approach promises to yield new insights into cell locomotion. 相似文献
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Eisenberg B 《Biophysical journal》2003,85(6):3427-3428
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How does tmRNA move through the ribosome? 总被引:2,自引:0,他引:2
Ivanov PV Zvereva MI Shpanchenko OV Dontsova OA Bogdanov AA Aglyamova GV Lim VI Teraoka Y Nierhaus KH 《FEBS letters》2002,514(1):55-59
To test the structure of tmRNA in solution, cross-linking experiments were performed which showed two sets of cross-links in two different domains of tmRNA. Site-directed mutagenesis was used to search for tmRNA nucleotide bases that might form a functional analogue of a codon-anticodon duplex to be recognized by the ribosomal A-site. We demonstrate that nucleotide residues U85 and A86 from tmRNA are significant for tmRNA function and propose that they are involved in formation of a tmRNA element playing a central role in A-site recognition. These data are discussed in the frame of a hypothetical model that suggests a general scheme for the interaction of tmRNA with the ribosome and explains how it moves through the ribosome. 相似文献
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Simberloff D 《The American naturalist》2004,163(6):787-799
Because of the contingency and complexity of its subject matter, community ecology has few general laws. Laws and models in community ecology are highly contingent, and their domain is usually very local. This fact does not mean that community ecology is a weak science; in fact, it is the locus of exciting advances, with growing mechanistic understanding of causes, patterns, and processes. Further, traditional community ecological research, often local, experimental, and reductionist, is crucial in understanding and responding to many environmental problems, including those posed by global changes. For both scientific and societal reasons, it is not time to abandon community ecology. 相似文献
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Flexistyly is a recently documented stylar polymorphism involving both spatial and temporal segregation of sex roles within hermaphroditic flowers. Using the experimental manipulation of stigma movement in self-compatible Alpinia mutica, we tested the hypothesis that selection for reducing interference between male and female function drives the evolution and/or maintenance of stigma movement. In experimental arrays, anaflexistylous (protogynous) flowers served as pollen donors competing for mating opportunities on cataflexistylous (protandrous) flowers. The pollen donors were either manipulated so their stigmas could not move or were left intact, and their success was determined using allozymes to assess the paternity of recipient seeds. We found that manipulated flowers sired a significantly smaller proportion of seeds, showing that stigma movement in unmanipulated plants increased male fitness. This result was strongest under conditions in which pollen competition was expected to be highest, specifically when pollinators visited multiple donor plants before visiting recipient flowers. 相似文献
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Suzuki Keisuke Matsubara Takeo Sakuramoto Hirotaka Hirata Koichi 《Sleep and biological rhythms》2018,16(3):369-370
Sleep and Biological Rhythms - A 74-year-old man presented with creepy, dull and restless sensation of the legs for a year. The abnormal leg sensation occurred predominantly during rest and... 相似文献
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By comparing the shift of the absorption maxima when a visual pigment is converted to its lumirhodopsin photointermediate for two classes of pigments, we can infer whether or not the pigment's beta-ionone ring has left its binding site. We compare this shift for the long-wavelength sensitive visual pigment of chicken iodopsin (lambdamax = 571 nm), which has polar residues in the ring binding site that interact with the ring, with that for three pigments, which do not. We conclude that by the time the Lumi product of the pigment is formed, the ring has moved away from the ring binding site. 相似文献