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991.
Many microbial genomes have been sequenced in the recent years. Multiple genes encoding Rieske iron-sulfur proteins, which are subunits of cytochrome bc-type complexes or oxygenases, have been detected in many pro- and eukaryotic genomes. The diversity of substrates, co-substrates and reactions offers obvious explanations for the diversity of the low potential Rieske proteins associated with oxygenases, but the physiological significance of the multiple genes encoding high potential Rieske proteins associated with the cytochrome bc-type complexes remains elusive. For some organisms, investigations into the function of the later group of genes have been initiated. Here, we summarize recent finding on the characteristics and physiological functions of multiple high potential Rieske proteins in prokaryotes. We suggest that the existence of multiple high potential Rieske proteins in prokaryotes could be one way of allowing an organism to adapt their electron transfer chains to changing environmental conditions. 相似文献
992.
Effects of xylem sap flow on carbon dioxide efflux from stems of birch (Betula pendula Roth) 总被引:2,自引:1,他引:2
The effect of xylem sap flow in stems of mature Betula pendula Roth on radial CO2 efflux was studied from April to October 2001. Temperature-controlled respiration cuvettes allowed measurements of CO2 efflux without interference from temperature gradients between stem surface and sapwood. Variations of sap flow in different stem sectors, and in a given sector at different heights were analysed. Daytime reduction of CO2 efflux caused by sap flow was expressed as the difference between gross and apparent CO2 release. Gross CO2 release was calculated from Arrhenius-equations derived from night-time data records of the same day, which were free from interference by sap flow. In mid-July, daytime reductions of CO2 efflux reached 1.8–3.9 μmol CO2 m−2 g−1 xylem sap transpired. Assuming tree-specific maximum transpiration rates of 30 kg H2O d−1 this is up to 40% of gross CO2 release. In relation to photosynthetic CO2 fixation the endogenous supply of dissolved CO2 to the leaves acccounted for 0.5–3.7%. This study indicates a negative correlation between sap flow velocity and radial CO2 efflux from B. pendula stems. Periods of unbalanced CO2 partial pressures between aqueous and gaseous pathways during increase and decrease of sap flow seem to affect gaseous CO2 release through lenticels. It is concluded that CO2 efflux rates are not simply equivalent to respiration rates because of the interference of aqueous CO2 transport by xylem sap flow in the wood-body of trees. 相似文献
993.
Coronary blood flow is tightly coupled to myocardial oxygen consumption to maintain a consistently high level of myocardial
oxygen extraction. This tight coupling has been proposed to depend on periarteriolar, oxygen tension, signals released from
cardiomyocytes (adenosine acting on K
ATP
+
channels), and/or the endothelium (prostanoids, nitric oxide, endothelin [ET]) and autonomic influences (catecholamines),
but the contribution of each of these regulatory pathways and their interactions are still incompletely understood. Until
recently, experimental studies into the regulation of coronary blood flow during exercise were principally performed in the
dog. We have performed several studies on the regulation of vasomotor tone in coronary resistance vessels in chronically instrumented
exercising swine. These studies have shown that the coronary resistance vessels in swine lack significant α-adrenergic control,
but that these vessels are subject to β-adrenergic feed-forward control during exercise, which is aided by a parasympathetic
withdrawal. In addition, withdrawal of an ET-mediated vasoconstrictor influence also contributes to exercise-induced coronary
vasodilation. Coronary blood flow regulation by endothelial and metabolic vasodilator pathways contributes to resting vasomotor
tone regulation but does not appear to contribute to the exercise-induced coronary vasodilation. Furthermore, blockade of
one vasodilator pathway is not compensated by an increased contribution of the other vasodilator mechanisms, suggesting that
porcine coronary vasomotor control by endothelial and metabolic factors occurs in a linear additive rather than a nonlinear
synergistic fashion. 相似文献
994.
Johansson I Smith B Munn K Tsikolia N Elsner K Ernst D Siebert D 《Acta biotheoretica》2005,53(3):153-166
It is argued that medical science requires a classificatory system that (a) puts functions in the taxonomic center and (b)
does justice ontologically to the difference between the processes which are the realizations of functions and the objects
which are their bearers. We propose formulae for constructing such a system and describe some of its benefits. The arguments
are general enough to be of interest to all the life sciences. 相似文献
995.
Kreykenbohm V Wenzel D Antonin W Atlachkine V von Mollard GF 《European journal of cell biology》2002,81(5):273-280
Two mammalian proteins, vtila and vtilb, are homologous to the yeast Q-SNARE Vtilp which is part of several SNARE complexes in different transport steps. In vitro experiments suggest distinct functions for vtila and vtilb. Here we compared the subcellular localization of endogenous vtila and vtilb by immunofluorescence and immuno-electron microscopy. Both proteins had a distinct but overlapping localization. vtila was found predominantly on the Golgi and the TGN, vtilb mostly on tubules and vesicles in the TGN area and on endosomes. vti1a coimmunoprecipitated with VAMP-4, syntaxin 6, and syntaxin 16. These four SNAREs could assemble into a SNARE complex of conserved structure because one SNARE motif of each subgroup is present. vtila-beta, VAMP-4, syntaxin 6, and syntaxin 16 are coenriched with small synaptic vesicles and with clathrin-coated vesicles isolated from rat brain synaptosomes. Therefore, this SNARE complex may have a role in synaptic vesicle biogenesis or recycling. 相似文献
996.
Taraban VY Martin S Attfield KE Glennie MJ Elliott T Elewaut D Van Calenbergh S Linclau B Al-Shamkhani A 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(7):4615-4620
Activation of invariant NK T (iNKT) cells with the glycolipid alpha-galactosylceramide promotes CD8(+) cytotoxic T cell responses, a property that has been used to enhance the efficacy of antitumor vaccines. Using chimeric mice, we now show that the adjuvant properties of iNKT cells require that CD40 triggering and Ag presentation to CD8(+) T cells occur on the same APCs. We demonstrate that injection of alpha-galactosylceramide triggers CD70 expression on splenic T cell zone dendritic cells and that this is dependent on CD40 signaling. Importantly, we show that blocking the interaction between CD70 and CD27, its costimulatory receptor on T cells, abrogates the ability of iNKT cells to promote a CD8(+) T cell response and abolishes the efficacy of alpha-GalCer as an adjuvant for antitumor vaccines. These results define a key role for CD70 in linking the innate response of iNKT cells to the activation of CD8(+) T cells. 相似文献
997.
Most mammalian cells contain two types of mannose 6-phosphate (Man-6-P) receptors (MPRs): the 300 kDa cation-independent (CI) MPR and 46 kDa cation-dependent (CD) MPR. The two MPRs have overlapping function in intracellular targeting of newly synthesized lysosomal proteins, but both are required for efficient targeting. Despite extensive investigation, the relative roles and specialized functions of each MPR in targeting of specific proteins remain questions of fundamental interest. One possibility is that most Man-6-P glycoproteins are transported by both MPRs, but there may be subsets that are preferentially transported by each. To investigate this, we have conducted a proteomics analysis of serum from mice lacking either MPR with the reasoning that lysosomal proteins that are selectively transported by a given MPR should be preferentially secreted into the bloodstream in its absence. We purified and identified Man-6-P glycoproteins and glycopeptides from wild-type, CDMPR-deficient, and CIMPR-deficient mouse serum and found both lysosomal proteins and proteins not currently thought to have lysosomal function. Different mass spectrometric approaches (spectral count analysis of nanospray LC-MS/MS experiments on unlabeled samples and LC-MALDI/TOF/TOF experiments on iTRAQ-labeled samples) revealed a number of proteins that appear specifically elevated in serum from each MPR-deficient mouse. Man-6-P glycoforms of cellular repressor of E1A-stimulated genes 1, tripeptidyl peptidase I, and heparanase were elevated in absence of the CDMPR and Man-6-P glycoforms of alpha-mannosidase B1, cathepsin D, and prosaposin were elevated in the absence of the CIMPR. Results were confirmed by Western blot analyses for select proteins. This study provides a comparison of different quantitative mass spectrometric approaches and provides the first report of proteins whose cellular targeting appears to be MPR-selective under physiological conditions. 相似文献
998.
De Vos D Xu Y Aerts T Van Petegem F Van Beeumen JJ 《Biochemical and biophysical research communications》2008,372(1):40-44
Aspartate carbamoyltransferase (ATCase) is a paradigm for allosteric regulation of enzyme activity. B-class ATCases display very similar homotropic allosteric behaviour, but differ extensively in their heterotropic patterns. The ATCase from the thermoacidophilic archaeon Sulfolobus acidocaldarius, for example, is strongly activated by its metabolic pathway′s end product CTP, in contrast with Escherichia coli ATCase which is inhibited by CTP. To investigate the structural basis of this property, we have solved the crystal structure of the S. acidocaldarius enzyme in complex with CTP. Structure comparison reveals that effector binding does not induce similar large-scale conformational changes as observed for the E. coli ATCase. However, shifts in sedimentation coefficients upon binding of the bi-substrate analogue PALA show the existence of structurally distinct allosteric states. This suggests that the so-called “Nucleotide-Perturbation model” for explaining heterotropic allosteric behaviour, which is based on global conformational strain, is not a general mechanism of B-class ATCases. 相似文献
999.
Frequent genes in rare diseases: panel‐based next generation sequencing to disclose causal mutations in hereditary neuropathies 下载免费PDF全文
Maike F. Dohrn Nicola Glöckle Lejla Mulahasanovic Corina Heller Julia Mohr Christine Bauer Erik Riesch Andrea Becker Florian Battke Konstanze Hörtnagel Thorsten Hornemann Saranya Suriyanarayanan Markus Blankenburg Jörg B. Schulz Kristl G. Claeys Burkhard Gess Istvan Katona Andreas Ferbert Debora Vittore Alexander Grimm Stefan Wolking Ludger Schöls Holger Lerche G. Christoph Korenke Dirk Fischer Bertold Schrank Urania Kotzaeridou Gerhard Kurlemann Bianca Dräger Anja Schirmacher Peter Young Beate Schlotter‐Weigel Saskia Biskup 《Journal of neurochemistry》2017,143(5):507-522
1000.
Can the agricultural AquaCrop model simulate water use and yield of a poplar short‐rotation coppice? 下载免费PDF全文
Joanna A. Horemans Hanne Van Gaelen Dirk Raes Terenzio Zenone Reinhart Ceulemans 《Global Change Biology Bioenergy》2017,9(6):1151-1164
We calibrated and evaluated the agricultural model AquaCrop for the simulation of water use and yield of a short‐rotation coppice (SRC) plantation with poplar (Populus) in East Flanders (Belgium) during the second and the third rotation (first 2 years only). Differences in crop development and growth during the course of the rotations were taken into account during the model calibration. Overall, the AquaCrop model showed good performance for the daily simulation of soil water content (R2 of 0.57–0.85), of green canopy cover (R2 > 0.87), of evapotranspiration (ET; R2 > 0.76), and of potential yield. The simulated, total yearly water use of the SRC ranged between 55% and 85% of the water use of a reference grass ecosystem calculated under the same environmental conditions. Crop transpiration was between 67% and 93% of total ET, with lower percentages in the first than in the second year of each rotation. The observed (dry mass) yield ranged from 6.61 to 14.76 Mg ha?1 yr?1. A yield gap of around 30% was observed between the second and the third rotation, as well as between simulated and observed yield during the third rotation. This could possibly be explained by the expansion of the understory (weed) layer; the relative cover of understory weeds was 22% in the third year of the third rotation. The agricultural AquaCrop model simulated total water use and potential yield of the operational SRC in a reliable way. As the plantation was extensively managed, potential effects of irrigation and/or fertilization on ET and on yield were not considered in this study. 相似文献