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231.
Linda Näsvik Öjemyr Amandine Maréchal Henrik Vestin Brigitte Meunier Peter R. Rich Peter Brzezinski 《BBA》2014
We have studied internal electron transfer during the reaction of Saccharomyces cerevisiae mitochondrial cytochrome c oxidase with dioxygen. Similar absorbance changes were observed with this yeast oxidase as with the previously studied Rhodobacter sphaeroides and bovine mitochondrial oxidases, which suggests that the reaction proceeds along the same trajectory. However, notable differences were observed in rates and electron-transfer equilibrium constants of specific reaction steps, for example the ferryl (F) to oxidized (O) reaction was faster with the yeast (0.4 ms) than with the bovine oxidase (~ 1 ms) and a larger fraction CuA was oxidized with the yeast than with the bovine oxidase in the peroxy (PR) to F reaction. Furthermore, upon replacement of Glu243, located at the end of the so-called D proton pathway, by Asp the PR → F and F → O reactions were slowed by factors of ~ 3 and ~ 10, respectively, and electron transfer from CuA to heme a during the PR → F reaction was not observed. These data indicate that during reduction of dioxygen protons are transferred through the D pathway, via Glu243, to the catalytic site in the yeast mitochondrial oxidase. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. 相似文献
232.
Nitrification in fixed-bed reactors treating saline wastewater 总被引:2,自引:0,他引:2
Utomo Sudarno Stephan Bathe Josef Winter Claudia Gallert 《Applied microbiology and biotechnology》2010,85(6):2017-2030
Halophilic nitrifiers belonging to the genus Nitrosomonas and Nitrospira were enriched from seawater and marine sediment samples of the North Sea. The maximal ammonia oxidation rate (AOR) in batch
enrichments with seawater was 15.1 mg N L−1 day−1. An intermediate nitrite accumulation was observed. Two fixed-bed reactors for continuous nitrification with either polyethylene/clay
sinter lamellas (FBR A) or porous ceramic rings (FBR B) were run at two different ammonia concentrations, three different
ammonia loading rates (ALRs), ± pH adjustment, and at an increased upflow velocity. A better overall nitrification without
nitrite accumulation was observed in FBR B. However, FBR A revealed a higher AOR and nitrite oxidation rate of 6 and 7 mg N L−1 h−1, compared to FBR B with 5 and 5.9 mg N L−1 h−1, respectively. AORs in the FBRs were at least ten times higher than in suspended enrichment cultures. Whereas a shift within
the ammonia-oxidizing population in the genus Nitrosomonas at the subspecies level occurred in FBR B with synthetic seawater at an increasing ALR and a decreasing pH, the nitrite oxidizing
Nitrospira population apparently did not change. 相似文献
233.
Nora Wender Jan Hegermann Bettina Brunner Brigitte Nuscher Tim Bartels Armin Giese Klaus Beyer Stefan Eimer Konstanze F Winklhofer Christian Haass 《The EMBO journal》2010,29(20):3571-3589
Aggregation of α‐synuclein (αS) is involved in the pathogenesis of Parkinson's disease (PD) and a variety of related neurodegenerative disorders. The physiological function of αS is largely unknown. We demonstrate with in vitro vesicle fusion experiments that αS has an inhibitory function on membrane fusion. Upon increased expression in cultured cells and in Caenorhabditis elegans, αS binds to mitochondria and leads to mitochondrial fragmentation. In C. elegans age‐dependent fragmentation of mitochondria is enhanced and shifted to an earlier time point upon expression of exogenous αS. In contrast, siRNA‐mediated downregulation of αS results in elongated mitochondria in cell culture. αS can act independently of mitochondrial fusion and fission proteins in shifting the dynamic morphologic equilibrium of mitochondria towards reduced fusion. Upon cellular fusion, αS prevents fusion of differently labelled mitochondrial populations. Thus, αS inhibits fusion due to its unique membrane interaction. Finally, mitochondrial fragmentation induced by expression of αS is rescued by coexpression of PINK1, parkin or DJ‐1 but not the PD‐associated mutations PINK1 G309D and parkin Δ1–79 or by DJ‐1 C106A. 相似文献
234.
Alexandra Magro Christine Ducamp Felipe Ramon-Portugal Emilie Lecompte Brigitte Crouau-Roy Anthony Frederick George Dixon Jean-Louis Hemptinne 《Evolutionary ecology》2010,24(1):251-271
Faced with an ephemeral prey, aphidophagous ladybirds rely on the hydrocarbons present in the tracks of their larvae to choose
an unoccupied patch for egg laying. Although both conspecific and heterospecific larval tracks might deter females from oviposition,
the response to the later is often less striking. Several explanations have been suggested to account for this. In this paper
we tested the phylogeny hypothesis, which predicts that the chemical composition of the tracks of closely related species
of ladybirds will be more similar to one another than to those of more distantly related species. Qualitative and quantitative
information on the chemical nature of the larval tracks and a molecular phylogeny of seven species belonging to three different
genera are provided, and the congruence between these two sets of results assessed. The results confirm the phylogeny hypothesis
and infer a gradual mode of evolution of these infochemicals. 相似文献
235.
Over the past decades, genetic analyses performed in vertebrate and invertebrate organisms deciphered numerous cellular and molecular mechanisms deployed during sexual development and identified genetic circuitries largely shared among bilaterians. In contrast, the functional analysis of the mechanisms that support regenerative processes in species randomly scattered among the animal kingdom, were limited by the lack of genetic tools. Consequently, unifying principles explaining how stress and injury can lead to the reactivation of a complete developmental program with restoration of original shape and function remained beyond reach of understanding. Recent data on cell plasticity suggest that beside the classical developmental approach, the analysis of homeostasis and asexual reproduction in adult organisms provides novel entry points to dissect the regenerative potential of a given species, a given organ or a given tissue. As a clue, both tissue homeostasis and regeneration dynamics rely on the availability of stem cells and/or on the plasticity of differentiated cells to replenish the missing structure. The freshwater Hydra polyp provides us with a unique model system to study the intricate relationships between the mechanisms that regulate the maintenance of homeostasis, even in extreme conditions (starvation and overfeeding) and the reactivation of developmental programs after bisection or during budding. Interestingly head regeneration in Hydra can follow several routes according to the level of amputation, suggesting that indeed the homeostatic background dramatically influences the route taken to bridge injury and regeneration. Mol. Reprod. Dev. 77:837–855, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
236.
Roland Müller Kurt Strässle Brigitte Wirth 《Journal of electromyography and kinesiology》2010,20(5):845-850
The validity of the Sorensen test as a measure for back muscle endurance is controversial due to a possible impact of hip extensor muscles. The aim of this study was to investigate the criterion validity of an alternative test (Ito test) compared to the Sorensen test. Both procedures were performed by 29 healthy subjects (11 women) for 5 s and until exhaustion (randomized order). EMG activity was measured from 3 lumbar back and 3 hip extensor muscles. Muscular involvement in test positions was calculated as percentage of maximal voluntary contraction (MVC). Muscle fatigue was determined by the normalized regression coefficient of the median frequencies of the EMG power spectrum (NMFslope). Prediction of holding time by NMFslope values was investigated using regression analysis. In the test positions, the hamstring muscles were activated to a higher MVC percentage in the Sorensen than in the Ito test, while the iliocostalis muscle was less activated. Similarly, the iliocostalis (p = 0.006) and the multifidi muscles (p = 0.03) significantly contributed to predict holding time in the Ito test, whereas the multifidi muscles (p = 0.001) and the semitendinosus muscle (p = 0.046) did so in the Sorensen test. The results of this study indicate that the Ito test might present a valuable alternative for testing back muscle endurance in LBP patients. 相似文献
237.
Bouke C. de Jong Ifedayo Adetifa Brigitte Walther Philip C. Hill Martin Antonio Martin Ota & Richard A. Adegbola 《FEMS immunology and medical microbiology》2010,58(1):102-105
Mycobacterium africanum (MAF) is a common cause of human pulmonary tuberculosis in West Africa. We previously described phenotypic differences between MAF and Mycobacterium tuberculosis (MTB) among 290 patients. In the present analysis, we compared 692 tuberculosis patients infected with the two most common lineages within the (MTB) complex found in the Gambia, namely MAF West African type 2 (39% prevalence) and Euro-American MTB (55% prevalence). We identified additional phenotypic differences between infections with these two organisms. MAF patients were more likely to be older and HIV infected. In addition, they had worse disease on chest X-ray, despite complaining of cough for an equal duration, and were more likely severely malnourished. In this cohort, the prevalence of MAF did not change significantly over a 7-year period. 相似文献
238.
Bruno Meunier Brigitte Picard Thierry Astruc Roland Labas 《Histochemistry and cell biology》2010,134(3):307-317
An accurate characterisation of muscle fibres is essential for studying muscle plasticity. During some transient events such
as ageing, myogenesis, physical activity or conversion of muscle to meat, the morphological parameters and/or the fibre type
distribution may change. Nowadays, this information is generally obtained using immunohistology techniques, but these analyses
are acknowledged to be laborious and time-consuming. In fact, each myofibre, from thousands, must be measured individually
and its expression profile in response to different anti-myosin antibodies must be established step by step. In this paper,
we describe a new histological approach using double-labelling (laminin, myosin) serial sections, fluorescence microscopy
visualisation and, finally, semi-automatic image analysis. The goal of the study was to propose a tool allowing faster fibre
type characterisation, including the identification of hybrid fibres from pure ones. The steps in the image processing prone
to subjectivity have been fully automated. On the other hand, the expert retained control of all image analysis procedures
requiring visual diagnosis. The tool that we developed with the Visilog software allowed a rapid and objective fibre typing
and morphometric characterisation of two different bovine muscles. The results were in agreement with our previous histological
and densitometric assays. The method and the tool proved to be potentially more efficient than other techniques used in our
institute or described in the literature. A more global evaluation will be considered in other laboratories as well as on
other animal species. 相似文献
239.
240.
The biosynthesis of the volatiles 2,5‐ and 2,6‐diisopropylpyrazine ( 2 and 3 , resp.) released by the myxobacteria Nannocystis exedens subsp. cinnabarina (Na c29) and Chondromyces crocatus (strains Cm c2 and Cm c5) was studied. Isotopically labeled precursors and proposed pathway intermediates were fed to agar plate cultures of the myxobacteria. Subsequently, the volatiles were collected by use of a closed loop stripping apparatus (CLSA), and incorporation into the pyrazines was followed by GC/MS analysis. [2H8]Valine was smoothly incorporated into both pyrazines clearly establishing their origin from the amino acid pool. The cyclic dipeptide valine anhydride ( 16 ) – a potential intermediate on the biosynthetic pathway to branched dialkylpyrazines – was synthesized containing 2H1 labels in specific positions. Feeding of [2H16]‐ 16 and [2H12]‐ 16 in both valine subunits mainly resulted in the formation of pyrazines derived from only one labeled amino acid, whereas only traces of the expected pyrazines with two labeled subunits were found. To investigate the origin of nitrogen in the pyrazines, a feeding experiment with [15N]valine was performed, resulting in the incorporation of the 15N label. The results contradict a biosynthetic pathway via cyclic dipeptides, but rather point to a pathway on which valine is reduced to valine aldehyde. Its dimerization to 2,5‐diisopropyldihydropyrazine 36 and subsequent oxidation results in 2 . The proposed biosynthetic pathway neatly fits the results of earlier labeling studies and also explains the formation of the regioisomer 2,6‐diisopropylpyrazine 3 by isomerization during the first condensation step of two molecules valine aldehyde. A general biosynthetic pathway to different classes of pyrazines is presented. 相似文献