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61.
Liverworts are well supported as the sister group to all other land plants (embryophytes) by molecular data. Observations
strongly supporting this earliest dichotomy in embryophyte evolution are the strikingly different introns occurring in the
mitochondrial DNAs of liverworts versus non-liverwort embryophytes (NLE), including the mosses. A final conclusion on the
most basal lineages of mosses, for which genera such as Sphagnum and Takakia are the most likely candidates, is lacking. We have now investigated cox1i624, a mitochondrial group I intron conserved between
the moss Physcomitrella patens and the liverwort Marchantia polymorpha. Focusing on a sampling of liverwort and moss genera, which had previously been identified as early branching taxa in their
respective clades, we find that group I intron cox1i624 is universally conserved in all 33 mosses and 11 liverworts investigated.
The group I intron core secondary structure is well conserved between the two ancient land plant clades. However, whereas
dramatic size reductions are seen in the moss phylogeny, exactly the opposite is observed for liverworts. The cox1i624g1 locus
was used for phylogenetic tree reconstruction also in combination with data sets of nad5i753g1 as well as chloroplast loci
rbcL and rps4. The phylogenetic analyses revealed (i) very good support for the Treubiopsida as sister clade to all other liverworts,
(ii) a sister group relationship of the nematodontous Tetraphidopsida and Polytrichopsida and (iii) two rivalling hypotheses
about the basal-most moss genus with mitochondrial loci suggesting an isolated Takakia as sister to all other mosses and chloroplast loci indicating a Takakia–Sphagnum clade. 相似文献
62.
Hölzer A Schröder C Woiczinski M Sadoghi P Müller PE Jansson V 《Journal of biomechanics》2012,45(3):602-604
The joint fluid mechanics and transport of wear particles in the prosthetic hip joint were analyzed for subluxation and flexion motion using computational fluid dynamics (CFD). The entire joint space including a moving capsule boundary was considered. It was found that particles suspended in the joint space are drawn into the joint gap between prosthesis cup and head during subluxation, which was also documented by Lundberg et al. (2007; Journal of Biomechanics 40, 1676-1685), however, wear particles remain in the joint gap. Wear particles leave the joint gap during flexion and can finally migrate to the proximal boundaries including the acetabular bone, where the particle deposition can cause osteolysis according to the established literature. Thus, the present study supports the theory of polyethylene wear particle induced osteolysis of the acetabular bone as a major factor in the loosening of hip prosthesis cups. 相似文献
63.
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65.
Volkmar U Groth-Malonek M Heinrichs J Muhle H Polsakiewicz M Knoop V 《Plant biology (Stuttgart, Germany)》2012,14(2):382-391
Liverworts occupy a pivotal position in land plant (embryophyte) phylogeny as the presumed earliest-branching major clade, sister to all other land plants, including the mosses, hornworts, lycophytes, monilophytes and seed plants. Molecular support for this earliest dichotomy in land plant phylogeny comes from strikingly different occurrences of introns in mitochondrial genes distinguishing liverworts from all other embryophytes. Exceptionally, however, the nad5 gene--the mitochondrial locus hitherto used most widely to elucidate early land plant phylogeny--carries a group I type intron that is shared between liverworts and mosses. We here explored whether a group II intron, the other major type of organellar intron, would similarly be conserved in position across the entire diversity of extant liverworts and could be of use for phylogenetic analyses in this supposedly most ancient embryophyte clade. To this end, we investigated the nad4 gene as a candidate locus possibly featuring different introns in liverworts as opposed to the non-liverwort embryophyte (NLE) lineage. We indeed found group II intron nad4i548 universally conserved in a wide phylogenetic sampling of 55 liverwort taxa, confirming clade specificity and surprising evolutionary stability of plant mitochondrial introns. As expected, intron nad4i548g2 carries phylogenetic information in its variable sequences, which confirms and extends previous cladistic insights on liverwort evolution. We integrate the new nad4 data with those of the previously established mitochondrial nad5 and the chloroplast rbcL and rps4 genes and present a phylogeny based on the fused datasets. Notably, the phylogenetic analyses suggest a reconsideration of previous phylogenetic and taxonomic assignments for the genera Calycularia and Mylia and resolve a sister group relationship of Ptilidiales and Porellales. 相似文献
66.
Schneider J Rupp O Trost E Jaenicke S Passoth V Goesmann A Tauch A Brinkrolf K 《FEMS yeast research》2012,12(3):382-386
The ascomycetous yeast Wickerhamomyces anomalus (formerly Pichia anomala and Hansenula anomala) exhibits antimicrobial activities and flavoring features that are responsible for its frequent association with food, beverage and feed products. However, limited information on the genetic background of this yeast and its multiple capabilities are currently available. Here, we present the draft genome sequence of the neotype strain W.?anomalus DSM 6766. On the basis of pyrosequencing, a de novo assembly of this strain resulted in a draft genome sequence with a total size of 25.47?Mbp. An automatic annotation using RAPYD generated 11?512 protein-coding sequences. This annotation provided the basis to analyse metabolic capabilities, phylogenetic relationships, as well as biotechnologically important features and yielded novel candidate genes of W.?anomalus DSM 6766 coding for proteins participating in antimicrobial activities. 相似文献
67.
Kuhlmann CR Gerigk M Bender B Closhen D Lessmann V Luhmann HJ 《Life sciences》2008,82(25-26):1281-1287
Glutamate is an important excitatory amino acid in the central nervous system. Under pathological conditions glutamate levels dramatically increase. Aim of the present study was to examine whether the HMG-CoA inhibitor fluvastatin prevents glutamate-induced blood-brain-barrier (BBB) disruption. Measurements of transendothelial electrical resistance (TEER) were performed to analyze BBB integrity in an in vitro co-culture model of brain endothelial and glial cells. Myosin light chain (MLC) phosphorylation was detected by immunohistochemistry, or using the in-cell western technique. Intracellular Ca2+ and reactive oxygen species (ROS) levels were analyzed using the fluorescence dyes Ca-green or DCF. Glutamate induced a time- (1-3 h) and concentration- (0.25-1 mmol/l) dependent decrease of TEER values that was blocked by the NMDA-receptor antagonist MK801, the Ca2+ chelator BAPTA, the NAD(P)H-oxidase inhibitor apocynin and the MLC-kinase inhibitor ML-7. Furthermore we observed a concentration-dependent increase of intracellular Ca2+ and ROS after glutamate application. Glutamate caused an increase of MLC phosphorylation that was antagonized by apocynin, or BAPTA, indicating that Ca2+ and ROS signaling is involved in the activation of the contractile machinery. Fluvastatin (10-25 micromol/l) completely abolished the glutamate-induced barrier disruption and oxidative stress. The BBB-protecting effect of fluvastatin was completely lost if the cells were treated with the nitric oxide (NO) synthase inhibitor L-NMMA (300 micromol/l). In the present study we demonstrated that glutamate-induced BBB disruption involves Ca2+ signalling via NMDA receptors, which is followed by an increased ROS generation by the NAD(P)H-oxidase. This oxidative stress then activates the MLC kinase. Fluvastatin preserves barrier function in a NO-dependent way and reduces glutamate-induced oxidative stress. 相似文献
68.
Kaminski T Siebrasse JP Gieselmann V Kubitscheck U Kappler J 《Glycoconjugate journal》2008,25(6):555-560
Hyaluronan is an important soluble component of the extracellular matrix of many tissues with well known space-filling, lubricating
and signaling functions. As such, hyaluronan can regulate cell adhesion, migration, differentiation and proliferation. Ultrastructural
studies showed the existence of fibers and networks of hyaluronan molecules at surfaces, while bulk studies of hyaluronan
in solution indicated that the polymer forms random coils. Here, we show that single hyaluronan molecules can be visualized
and tracked in three-dimensional samples at room temperature in aqueous buffer. Using a wide-field fluorescence microscope
equipped with laser excitation and an sensitive and fast EMCCD camera for fluorescence detection, single FITC-labeled hyaluronan
molecules from rooster comb were detected in aqueous solutions. Freely moving hyaluronan-FITC could be tracked over up to
20 images acquired at a frame rate of 98 Hz. Analysis of the trajectories revealed Brownian motion of hyaluronan in tris-buffered
saline with an average diffusion coefficient D = 3.0 ± 0.2 μm2/s. These observations confirm the concept that hyaluronan molecules form random coils in solution. The possibility of following
the tracks of single hyaluronan molecules in solution facilitates the analysis of processes that lead to the formation of
more organized forms of hyaluronan and its interactions with cells with very high spatial and temporal accuracy.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
69.
Johan Van de Koppel Richard D. Bardgett Janne Bengtsson Claudino Rodriguez-Barrueco Max Rietkerk Martin J. Wassen Volkmar Wolters 《Ecosystems》2005,8(7):801-807
Food chain models have dominated empirical studies of trophic interactions in the past decades, and have lead to important
insights into the factors that control ecological communities. Despite the importance of food chain models in instigating
ecological investigations, many empirical studies still show a strong deviation from the dynamics that food chain models predict.
We present a theoretical framework that explains some of the discrepancies by showing that trophic interactions are likely
to be strongly influenced by the spatial configuration of consumers and their resources. Differences in the spatial scale
at which consumers and their resources function lead to uncoupling of the population dynamics of the interacting species,
and may explain overexploitation and depletion of resource populations. We discuss how changed land use, likely the most prominent
future stress on natural systems, may affect food web dynamics by interfering with the scale of interaction between consumers
and their resource. 相似文献
70.
Most Serratia marcescens strains produce a new type of cytolysin (hemolysin) which is also found in other Serratia species. The hemolytic polypeptide ShlA (M(r) 162 101) is secreted across the outer membrane through the help of the ShlB protein which also involves conversion of an inactive precursor in an hemolytically active form. Both proteins are synthesized with signal sequences which are released during export across the cytoplasmic membrane. Mutants expressing inactive ShlB derivatives are impaired in activation and secretion suggesting a tight coupling between both processes. The region of ShlA for activation and secretion is confined to the N-terminal 16% of the polypeptide which contains the sequence NPNG which is also found in the Proteus hemolysin, the Bordetella pertussis filamentous hemagglutinin and two highly expressed outer membrane proteins of Haemophilus influenzae. Substitution of the first asparagine (N) residue by isoleucine converts the Serratia hemolysin into an inactive secretion incompetent form. It is concluded that this region is recognized by ShlB for activation and secretion of ShlA. The Serratia hemolysin forms defined pores in erythrocyte membranes. 相似文献