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981.
HERMES PÉREZ‐HÉRNANDEZ ANNE DAMON JAVIER VALLE‐MORA DANIEL SÁNCHEZ‐GUILLEN 《Botanical journal of the Linnean Society. Linnean Society of London》2011,165(3):251-266
Looking for clues to explain the low rate and unpredictability of the pollination of allogamous, epiphytic orchids in the context of the success of the orchid family in general, we compared the pollination of two miniature twig epiphytes in Mexico: Notylia barkeri, a ‘weedy’, rewarding species, and Erycina crista‐galli, a rare, deceptive species. We measured the effects of the spatial organization of the flowers and various parameters of visibility and height above the ground in relation to the spatial organization of the seed capsules (which retrospectively measures the activity of the pollinators). The spatial presentation of the flowers of E. crista‐galli explained only 5% of the distribution of the seed capsules. For N. barkeri, with compound flowers, the spatial presentation, considering individual flowers or inflorescences, explained 12% and 45% of the distribution of the seed capsules, respectively, and all other interactions between the variables were insignificant. Both the deceptive and reward strategies resulted in the production of large numbers of seeds despite a low pollination percentage (1–5%). Notylia barkeri produced 11.8 (2005–6) and 53.7 (2007–8) times more seeds in total than E. crista‐galli. Furthermore, unlike E. crista‐galli, N. barkeri responded to loss of individuals after high winds with an increased production of flowers per plant. We suggest that orchids have evolved to specialize in chance, and instead of maximizing pollinator attraction, they maximize the seed production resulting from every casual encounter. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 251–266. 相似文献
982.
Smirnova OA Ivanov AV Ivanova ON Valuev-Éllison VT Kochetkov SN 《Molekuliarnaia biologiia》2011,45(1):127-141
Hepatitis C virus is one of the most spread and dangerous human pathogens. In most cases hepatitis C develops into chronic diseases which in many cases escape antiviral therapy and is associated with contributed to progression of various virus-associated organ damage and disorders including liver fibrosis, steatosis and hepatocellular carcinoma. Many of these diseases are currently linked to oxidative and ER stresses induced by the viral proteins. At the same time, hepatitis C virus disturbs systems protecting cells from these stresses, thus avoiding their effect on processes of the virus life cycle. Here, we have analyzed recent data on mechanisms of the cellular defense system functioning in infected and uninfected cells. In addition, major data on the hepatitis C virus genome structure and main functions of the virus proteins have been summarized briefly. 相似文献
983.
ANDRÉ LINHARES ROSSI CLAUDIA AUGUSTA DE MORAES RUSSO ANTONIO MATEO SOLÉ‐CAVA HANS TORE RAPP MICHELLE KLAUTAU 《Zoological Journal of the Linnean Society》2011,163(4):1026-1034
Some of the morphological characters used in Porifera taxonomy have often been shown to be inconsistent. In the present study, we tested the phylogenetic coherence of currently used taxonomic characters of the calcarean genus Clathrina. For this, 20 species of Clathrina and three other calcinean genera (Ascandra, Guancha, and Leucetta) were sequenced for the ITS and D2 region of the 28S ribosomal DNA. Maximum‐likelihood and maximum‐parsimony algorithms were used to reconstruct phylogenetic trees. Deep divergences were observed in our tree and Clathrina was shown to be paraphyletic. The major split in our topology showed a clear‐cut distinction between sponges with and without tetractine spicules. Moreover, a group of yellow‐coloured Clathrina was clearly separated from the remaining white‐coloured species. Our results show that the presence of diactines, water‐collecting tubes, the degree of cormus anastomosis, and actine shapes do not correlate with the major clades of the calcinean phylogeny. On the other hand, the presence of tripods, the absence of tetractines, and the presence of spines in the apical actine of tetractines seem to be good synapomorphies for clades in our tree. Our results demonstrate that skeleton characters can be reliably used in higher level taxonomy in Clathrinida. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1026–1034. 相似文献
984.
985.
Fluorescent tags are extensively used for the diagnostic, labeling and marking in vivo and in vitro systems. In this study, fluorescent nanoparticles with Er/Yb lightning center were tested on neutrophilic granulocytes. The main purpose was to idenfity possible toxic effect. The negative impact of fluorophores on the metabolism of neutrophilic and their enzyme systems, on the receptor-mediated cell responses and on the rigidity of cell membranes was shown. The viability of neutrophils (estimated with the use of propidium iodide) after 2 hours of incubation with the fluorescent nanoparticles in concentrations of 10(-4) and 10(-3) mM was 27.0 +/- 6.6 and 19.07 +/- 3.34 %, respectively. 相似文献
986.
FRANÇOIS GUILLEMETTE CHARLES VALLÉE ANDREA BERTOLO PIERRE MAGNAN 《Freshwater Biology》2011,56(6):1017-1029
1. Despite the great interest in characterising fish reproductive habitat, the relationship between the selection of a given spawning site and individual fitness has not been experimentally tested. 2. In this study, we used an in situ experimental approach to determine (i) the relative contribution of substrate characteristics as well as hydrological and physicochemical variables to small‐scale redd site selection by brook charr, Salvelinus fontinalis (Mitchill) and (ii) if hatching and emergence success, used as a surrogate of fitness, are improved in selected compared to non‐selected sites in both lake and stream habitats. 3. Our results show that upwelling groundwater flow was always significantly higher in selected than in non‐selected sites in both lake and stream habitats. We found no significant difference in the mean geometric substrate diameter and no consistent differences in substrate composition between selected and non‐selected sites. Oxygen concentration was higher (significantly so in three of four comparisons) and conductivity tended to be lower in selected than in non‐selected sites, while temperature showed no significant or consistent variations. We found a significant positive relationship between the selection of a given spawning habitat and hatching and emergence success in these systems. 4. These results show that the main cue that brook charr use to select their spawning sites is upwelling groundwater in lake and stream habitats, and that active selection of these sites increases individual fitness. This suggests that natural selection acted on the same cues in lentic and lotic environments; this could have been highly adaptive in a species that used both habitats as colonisation routes after the last glaciation. 相似文献
987.
Morlighem JÉ Aoki S Kishima M Hanami M Ogawa C Jalloh A Takahashi Y Kawai Y Saga S Hayashi E Ban T Izumi S Wada A Mano M Fukunaga M Kijima Y Shiomi M Inoue K Hata T Koretsune Y Kudo K Himeno Y Hirai A Takahashi K Sakai-Tagawa Y Iwatsuki-Horimoto K Kawaoka Y Hayashizaki Y Ishikawa T 《PloS one》2011,6(4):e18956
Background
Pandemic influenza A(H1N1) virus infection quickly circulated worldwide in 2009. In Japan, the first case was reported in May 2009, one month after its outbreak in Mexico. Thereafter, A(H1N1) infection spread widely throughout the country. It is of great importance to profile and understand the situation regarding viral mutations and their circulation in Japan to accumulate a knowledge base and to prepare clinical response platforms before a second pandemic (pdm) wave emerges.Methodology
A total of 253 swab samples were collected from patients with influenza-like illness in the Osaka, Tokyo, and Chiba areas both in May 2009 and between October 2009 and January 2010. We analyzed partial sequences of the hemagglutinin (HA) and neuraminidase (NA) genes of the 2009 pdm influenza virus in the collected clinical samples. By phylogenetic analysis, we identified major variants of the 2009 pdm influenza virus and critical mutations associated with severe cases, including drug-resistance mutations.Results and Conclusions
Our sequence analysis has revealed that both HA-S220T and NA-N248D are major non-synonymous mutations that clearly discriminate the 2009 pdm influenza viruses identified in the very early phase (May 2009) from those found in the peak phase (October 2009 to January 2010) in Japan. By phylogenetic analysis, we found 14 micro-clades within the viruses collected during the peak phase. Among them, 12 were new micro-clades, while two were previously reported. Oseltamivir resistance-related mutations, i.e., NA-H275Y and NA-N295S, were also detected in sporadic cases in Osaka and Tokyo. 相似文献988.
The trade-off hypothesis proposes that the evolution of pathogens' virulence is shaped by a link between virulence and contagiousness. This link is often assumed to come from the fact that pathogens are contagious only if they can reach high parasitic load in the infected host. In this paper we present an experimental test of the hypothesis that selection on fast replication can affect virulence. In a serial passage experiment, we selected 80 lines of the bacterial insect-pathogen Xenorhabdus nematophila to multiply fast in an artificial culture medium. This selection resulted in shortened lag phase in our selected bacteria. We then injected these bacteria into insects and observed an increase in virulence. This could be taken as a sign that virulence in Xenorhabdus is linked to fast multiplication. But we found, among the selected lineages, either no link or a positive correlation between lag duration and virulence: the most virulent bacteria were the last to start multiplying. We then surveyed phenotypes that are under the control of the flhDC super regulon, which has been shown to be involved in Xenorhabdus virulence. We found that, in one treatment, the flhDC regulon has evolved rapidly, but that the changes we observed were not connected to virulence. All together, these results indicate that virulence is, in Xenorhabdus as in many other pathogens, a multifactorial trait. Being able to grow fast is one way to be virulent. But other ways exist which renders the evolution of virulence hard to predict. 相似文献
989.
Varga Z Juhász T Matta C Fodor J Katona É Bartok A Oláh T Sebe A Csernoch L Panyi G Zákány R 《PloS one》2011,6(11):e27957
Background
Understanding the key elements of signaling of chondroprogenitor cells at the earliest steps of differentiation may substantially improve our opportunities for the application of mesenchymal stem cells in cartilage tissue engineering, which is a promising approach of regenerative therapy of joint diseases. Ion channels, membrane potential and Ca2+-signaling are important regulators of cell proliferation and differentiation. Our aim was to identify such plasma membrane ion channels involved in signaling during chondrogenesis, which may serve as specific molecular targets for influencing chondrogenic differentiation and ultimately cartilage formation.Methodology/Principal Findings
Using patch-clamp, RT-PCR and Western-blot experiments, we found that chondrogenic cells in primary micromass cell cultures obtained from embryonic chicken limb buds expressed voltage-gated NaV1.4, KV1.1, KV1.3 and KV4.1 channels, although KV1.3 was not detectable in the plasma membrane. Tetrodotoxin (TTX), the inhibitor of NaV1.4 channels, had no effect on cartilage formation. In contrast, presence of 20 mM of the K+ channel blocker tetraethyl-ammonium (TEA) during the time-window of the final commitment of chondrogenic cells reduced KV currents (to 27±3% of control), cell proliferation (thymidine incorporation: to 39±4.4% of control), expression of cartilage-specific genes and consequently, cartilage formation (metachromasia: to 18.0±6.4% of control) and also depolarized the membrane potential (by 9.3±2.1 mV). High-frequency Ca2+-oscillations were also suppressed by 10 mM TEA (confocal microscopy: frequency to 8.5±2.6% of the control). Peak expression of TEA-sensitive KV1.1 in the plasma membrane overlapped with this period. Application of TEA to differentiated chondrocytes, mainly expressing the TEA-insensitive KV4.1 did not affect cartilage formation.Conclusions/Significance
These data demonstrate that the differentiation and proliferation of chondrogenic cells depend on rapid Ca2+-oscillations, which are modulated by KV-driven membrane potential changes. KV1.1 function seems especially critical during the final commitment period. We show the critical role of voltage-gated cation channels in the differentiation of non-excitable cells with potential therapeutic use. 相似文献990.
Daga Vanessa S. Olden Julian D. Gubiani Éder A. Piana Pitágoras A. Padial André A. Vitule Jean R. S. 《Hydrobiologia》2020,847(18):3759-3772
Hydrobiologia - The conservation challenges facing freshwater ecosystems necessitate broadening our science from understanding individual species loss to anticipating multi-faceted changes to... 相似文献