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排序方式: 共有365条查询结果,搜索用时 15 毫秒
71.
The ability of probiotic bacteria to bind to human intestinal mucus 总被引:22,自引:0,他引:22
72.
Vesa Aho Sami Salminen Salla Mattola Alka Gupta Felix Flomm Beate Sodeik Jens B. Bosse Maija Vihinen-Ranta 《PLoS pathogens》2021,17(12)
Herpes simplex virus capsids are assembled and packaged in the nucleus and move by diffusion through the nucleoplasm to the nuclear envelope for egress. Analyzing their motion provides conclusions not only on capsid transport but also on the properties of the nuclear environment during infection. We utilized live-cell imaging and single-particle tracking to characterize capsid motion relative to the host chromatin. The data indicate that as the chromatin was marginalized toward the nuclear envelope it presented a restrictive barrier to the capsids. However, later in infection this barrier became more permissive and the probability of capsids to enter the chromatin increased. Thus, although chromatin marginalization initially restricted capsid transport to the nuclear envelope, a structural reorganization of the chromatin counteracted that to promote capsid transport later. Analyses of capsid motion revealed that it was subdiffusive, and that the diffusion coefficients were lower in the chromatin than in regions lacking chromatin. In addition, the diffusion coefficient in both regions increased during infection. Throughout the infection, the capsids were never enriched at the nuclear envelope, which suggests that instead of nuclear export the transport through the chromatin is the rate-limiting step for the nuclear egress of capsids. This provides motivation for further studies by validating the importance of intranuclear transport to the life cycle of HSV-1. 相似文献
73.
Apiradee Pothipongsa Saowarath Jantaro Tiina A. Salminen Aran Incharoensakdi 《World journal of microbiology & biotechnology》2017,33(4):72
Spermidine synthase (Spds) catalyzes the formation of spermidine by transferring the aminopropyl group from decarboxylated S-adenosylmethionine (dcSAM) to putrescine. The Synechococcus spds gene encoding Spds was expressed in Escherichia coli. The purified recombinant enzyme had a molecular mass of 33 kDa and showed optimal activity at pH 7.5, 37?°C. The enzyme had higher affinity for dcSAM (K m, 20 µM) than for putrescine (K m, 111 µM) and was highly specific towards the diamine putrescine with no activity observed towards longer chain diamines. The three-dimensional structural model for Synechococcus Spds revealed that most of the ligand binding residues in Spds from Synechococcus sp. PCC 7942 are identical to those of human and parasite Spds. Based on the model, the highly conserved acidic residues, Asp89, Asp159 and Asp162, are involved in the binding of substrates putrescine and dcSAM and Pro166 seems to confer substrate specificity towards putrescine. 相似文献
74.
Sampo J. Lahtinen Miguel Gueimonde Arthur C. Ouwehand Johanna P. Reinikainen Seppo J. Salminen 《Applied microbiology》2005,71(3):1662-1663
The determination of bacterial viability in probiotic products is of economic, technological, and clinical significance. We compared four methods to enumerate three Bifidobacterium strains in fermented oat products during storage. A subpopulation of nonculturable cells retained a functional cell membrane typical of viable cells, indicating that probiotic bacteria become dormant during storage. 相似文献
75.
Tree resistance to Lymantria dispar caterpillars: importance and limitations of foliar tannin composition 总被引:1,自引:0,他引:1
Raymond V. Barbehenn Adam Jaros Grace Lee Cara Mozola Quentin Weir Juha-Pekka Salminen 《Oecologia》2009,159(4):777-788
The ability of foliar tannins to increase plant resistance to herbivores is potentially determined by the composition of the
tannins; hydrolyzable tannins are much more active as prooxidants in the guts of caterpillars than are condensed tannins.
By manipulating the tannin compositions of two contrasting tree species, this work examined: (1) whether increased levels
of hydrolyzable tannins increase the resistance of red oak (Quercus rubra L.), a tree with low resistance that produces mainly condensed tannins, and (2) whether increased levels of condensed tannins
decrease the resistance of sugar maple (Acer saccharum Marsh.), a tree with relatively high resistance that produces high levels of hydrolyzable tannins. As expected, when Lymantria dispar L. caterpillars ingested oak leaves coated with hydrolyzable tannins, levels of hydrolyzable tannin oxidation increased in
their midgut contents. However, increased tannin oxidation had no significant impact on oxidative stress in the surrounding
midgut tissues. Although growth efficiencies were decreased by hydrolyzable tannins, growth rates remained unchanged, suggesting
that additional hydrolyzable tannins are not sufficient to increase the resistance of oak. In larvae on condensed tannin-coated
maple, no antioxidant effects were observed in the midgut, and levels of tannin oxidation remained high. Consequently, neither
oxidative stress in midgut tissues nor larval performance were significantly affected by high levels of condensed tannins.
Post hoc comparisons of physiological mechanisms related to tree resistance revealed that maple produced not only higher levels
of oxidative stress in the midgut lumen and midgut tissues of L. dispar, but also decreased protein utilization efficiency compared with oak. Our results suggest that high levels of hydrolyzable
tannins are important for producing oxidative stress, but increased tree resistance to caterpillars may require additional
factors, such as those that produce nutritional stress. 相似文献
76.
The extent to which individual host trees maintain their relative quality over time may affect patterns of abundance, distribution and microevolution in herbivorous insects. In this study, we explore temporal consistency in the quality of oak Quercus robur foliage, using leaf‐chewing larvae of the moth Amphipyra pyramidea as our model herbivores. By utilising an artificial diet, we are able to isolate the impact of chemical contents from physical attributes, and thereby to ask to what extent purely chemical parameters create tree‐to‐tree differences in host quality, how consistent such differences are among trees between different parts of a single growth season, and to what extent individual moth larvae are able to compensate for chemical variation in food quality. We find that with physical traits controlled for, chemical traits suffice to create strong differences in larval growth rates between trees, and between larvae fed on young and mature foliage. Nevertheless, these initial differences are efficiently compensated for the fact that larvae with lower growth rates continue to grow for a longer time, and thereby end up at the same size as larvae with high growth rates. At the pupal stage, we could no longer detect differences between either larvae fed foliage from different trees or between larvae fed young versus mature foliage – despite notably little variation among individuals within each group. Such compensatory responses were also reflected in patterns of consistency. The intraclass correlation for larval weight was relatively high (ρ=0.45), but lower for development time (ρ=0.26), and non‐existent for pupal weight (ρ=0.00). These results suggest that in terms of pupal mass, A. pyramidea is able to compensate more or less completely for differences in resource quality, that patterns of consistency vary with the specific trait examined, and that the net effect of spatiotemporal variation in host plant quality on herbivore fitness should be dissected by experiments aimed at different life history traits. If slow growth comes with high mortality, spatiotemporal patterns in resource quality may have a major impact on herbivore fitness; if not, the patterns may be nullified by efficient compensatory mechanisms. 相似文献
77.
The relationship among temporal variation in the availability of carotenoid-rich food, tissue carotenoid levels and breeding success are poorly known. We studied how diet quality and quantity affect the carotenoid profile and fledging success of great tit (Parus major) nestlings along a pollution gradient. We found declining seasonal trend in lutein concentration of caterpillars, which may be the explanation for the declining trend in nestlings' lutein concentration of plasma with season, despite the increase in caterpillar biomass. This may be because the biomass of most lutein-rich caterpillars (autumnal moths) decreased and less lutein-rich caterpillars (sawflies) increased during the breeding season. The temporal difference in occurrence of different caterpillar species means that peak lutein availability does not coincide with peak caterpillar abundance. However the positive association between total larval biomass and the number of great tit fledglings may suggest that fledging success depends more on total caterpillar availability than on lutein concentration of caterpillars. 相似文献
78.
Background
Previous work on the human auditory cortex has revealed areas specialized in spatial processing but how the neurons in these areas represent the location of a sound source remains unknown.Methodology/Principal Findings
Here, we performed a magnetoencephalography (MEG) experiment with the aim of revealing the neural code of auditory space implemented by the human cortex. In a stimulus-specific adaptation paradigm, realistic spatial sound stimuli were presented in pairs of adaptor and probe locations. We found that the attenuation of the N1m response depended strongly on the spatial arrangement of the two sound sources. These location-specific effects showed that sounds originating from locations within the same hemifield activated the same neuronal population regardless of the spatial separation between the sound sources. In contrast, sounds originating from opposite hemifields activated separate groups of neurons.Conclusions/Significance
These results are highly consistent with a rate code of spatial location formed by two opponent populations, one tuned to locations in the left and the other to those in the right. This indicates that the neuronal code of sound source location implemented by the human auditory cortex is similar to that previously found in other primates. 相似文献79.
Tapio Eeva Suvi Ruuskanen Juha-Pekka Salminen Eugen Belskii Antero J?rvinen Anvar Kerimov Erkki Korpim?ki Indrikis Krams Juan Moreno Chiara Morosinotto Raivo M?nd Markku Orell Anna Qvarnstr?m Heli Siitari Fred M. Slater Vallo Tilgar Marcel E. Visser Wolfgang Winkel Herwig Zang Toni Laaksonen 《Oecologia》2011,165(2):277-287
Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female??s diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards. The most southern population (which is also the one found at the highest altitude) also showed relatively low carotenoid levels. Concentrations of ??-carotene and zeaxanthin did not show any obvious geographical gradients. Egg yolks also contained proportionally more lutein and other xanthophylls in deciduous than in mixed or coniferous habitats. We suggest that latitudinal gradients in lutein and xanthophylls reflect the lower availability of lutein-rich food items in the northern F. hypoleuca populations and in montane southern populations, which start egg-laying earlier relative to tree phenology than the Central European populations. Similarly, among-habitat variation is likely to reflect the better availability of lutein-rich food in deciduous forests. Our study is the first to indicate that the concentration and profile of yolk carotenoids may show large-scale spatial variation among populations in different parts of the species?? geographical range. Further studies are needed to test the fitness effects of this geographical variation. 相似文献
80.
Ruiz L Gueimonde M Couté Y Salminen S Sanchez JC de los Reyes-Gavilán CG Margolles A 《FEMS microbiology letters》2011,314(2):125-130
The ability of Bifidobacterium longum to use intestinal mucus as a metabolizable source was characterized. Bifidobacterium longum biotype longum NCIMB8809 was grown in a chemically semi-defined medium supplemented with human intestinal mucus, and the cytoplasmic protein profiles and several glycosyl hydrolase activities were analysed and compared with those obtained from the same bacterium grown in the absence of mucus. We were able to identify 22 different proteins in the cytoplasmic fraction, of which nine displayed a different concentration in the presence of mucus. Among the proteins whose concentrations varied, we found specific enzymes that are involved in the response to different environmental conditions, and also proteins that mediate interaction with mucus in bacteria. Significant changes in some glycoside-hydrolysing activities were also detected. In addition, stable isotope labelling of amino acids in cell culture demonstrated that B. longum incorporates leucine from the glycoprotein matrix of mucin within its proteins. This study provides the first proteomic data regarding the interaction of B. longum with intestinal mucus, and contributes to the understanding of the behaviour of this intestinal species in its natural ecological niche. 相似文献