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Chemosensory event-related potentials (CSERP) can be used toexamine central nervous odor processing. An important questionfor understanding odor perception is how different concentrationsare processed. In the present study two odors were chosen whichactivate either the olfactory (linalool) or the trigeminal (menthol)system. Both odors were presented to 11 subjects in four differentconcentrations. Four subjects had to attend actively to theodors while the others perceived the odors under passive attention.The results showed that increased concentrations of the olfactorystimulus resulted in shorter latencies of the N1 component butdid not affect the amplitudes of the CSERP. However, the amplitudesof the stimulus dependent, exogenous components (N1, P2) increasedwith higher concentrations of the trigeminal stimulus. The amplitudeof the late positive complex, which reflects endogenous processes,was usually larger when the odorous stimuli had to be attendedto actively. It is concluded that olfactory intensity codingresults in a qualitatively different but not in a stronger neuronalresponse of the human brain. Chem. Senses 22: 9–26, 1997.  相似文献   
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Human-pathogenic Bartonella henselae causes cat scratch disease and vasculoproliferative disorders. An important pathogenicity factor of B. henselae is the trimeric autotransporter adhesin (TAA) Bartonella adhesin A (BadA), which is modularly constructed, consisting of a head, a long and repetitive neck-stalk module, and a membrane anchor. BadA is involved in bacterial autoagglutination, binding to extracellular matrix proteins and host cells, and in proangiogenic reprogramming. The slow growth of B. henselae and limited tools for genetic manipulation are obstacles for detailed examination of BadA and its domains. Here, we established a recombinant expression system for BadA mutants in Escherichia coli allowing functional analysis of particular BadA domains. Using a BadA mutant lacking 21 neck-stalk repeats (BadA HN23), the BadA HN23 signal sequence was exchanged with that of E. coli OmpA, and the BadA membrane anchor was additionally replaced with that of Yersinia adhesin A (YadA). Constructs were cloned in E. coli, and hybrid protein expression was detected by immunoblotting, fluorescence microscopy, and flow cytometry. Functional analysis revealed that BadA hybrid proteins mediate autoagglutination and binding to collagen and endothelial cells. In vivo, expression of this BadA construct correlated with higher pathogenicity of E. coli in a Galleria mellonella infection model.  相似文献   
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The mitochondrial contact site and cristae organization system (MICOS) mediates the formation of cristae, invaginations in the mitochondrial inner membrane. The highly diverged MICOS complex of the parasitic protist Trypanosoma brucei consists of nine subunits. Except for two Mic10‐like and a Mic60‐like protein, all subunits are specific for kinetoplastids. Here, we determined on a proteome‐wide scale how ablation of individual MICOS subunits affects the levels of the other subunits. The results reveal co‐regulation of TbMic10‐1, TbMic10‐2, TbMic16 and TbMic60, suggesting that these nonessential, integral inner membrane proteins form an interdependent network. Moreover, the ablation of TbMic34 and TbMic32 reveals another network consisting of the essential, intermembrane space‐localized TbMic20, TbMic32, TbMic34 and TbMic40, all of which are peripherally associated with the inner membrane. The downregulation of TbMic20, TbMic32 and TbMic34 also interferes with mitochondrial protein import and reduces the size of the TbMic10‐containing complexes. Thus, the diverged MICOS of trypanosomes contains two subcomplexes: a nonessential membrane‐integrated one, organized around the conserved Mic10 and Mic60, that mediates cristae formation, and an essential membrane‐peripheral one consisting of four kinetoplastid‐specific subunits, that is required for import of intermembrane space proteins.  相似文献   
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Sphagnum‐dominated bogs represent a unique yet widely distributed type of terrestrial ecosystem and strongly contribute to global biosphere functioning. Sphagnum is colonized by highly diverse microbial communities, but less is known about their function. We identified a high functional diversity within the Sphagnum microbiome applying an Illumina‐based metagenomic approach followed by de novo assembly and MG‐RAST annotation. An interenvironmental comparison revealed that the Sphagnum microbiome harbours specific genetic features that distinguish it significantly from microbiomes of higher plants and peat soils. The differential traits especially support ecosystem functioning by a symbiotic lifestyle under poikilohydric and ombrotrophic conditions. To realise a plasticity–stability balance, we found abundant subsystems responsible to cope with oxidative and drought stresses, to exchange (mobile) genetic elements, and genes that encode for resistance to detrimental environmental factors, repair and self‐controlling mechanisms. Multiple microbe–microbe and plant–microbe interactions were also found to play a crucial role as indicated by diverse genes necessary for biofilm formation, interaction via quorum sensing and nutrient exchange. A high proportion of genes involved in nitrogen cycle and recycling of organic material supported the role of bacteria for nutrient supply. 16S rDNA analysis indicated a higher structural diversity than that which had been previously detected using PCR‐dependent techniques. Altogether, the diverse Sphagnum microbiome has the ability to support the life of the host plant and the entire ecosystem under changing environmental conditions. Beyond this, the moss microbiome presents a promising bio‐resource for environmental biotechnology – with respect to novel enzymes or stress‐protecting bacteria.  相似文献   
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A tonoplast protein of 31 kDa apparent molecular mass (TpP 31) was isolated from two-dimensional gels. Amino acid sequences were determined from LysC endoproteinase-peptide fragments. Using degenerate oligonucleotides, a corresponding cDNA clone of 1034 bp was isolated from a barley leaf cDNA library. It encodes for subunit E of the vacuolar H+-ATPase, the first one identified in plants so far. The open reading frame extends over 681 bp, encoding a gene product of 227 amino acids and a calculated molecular weight of 26 228 g mol?1. Northern and Western blot analysis indicates constitutive expression of subunit E in all plant organs with only small effects of salt stress. Localization of TpP 31 at the tonoplast was confirmed in fractions of purified vacuolar membrane obtained by free-flow electrophoresis. Immunoprecipitation of newly synthesized 35S-labelled membrane proteins with anti-TpP 31 gave two additional bands with apparent molecular masses of about 53 and 62 kDa. Gel filtration after mild solubilization showed co-purification of TpP 31 with the 55 kDa subunit of the H+-ATPase. Both results provide evidence beyond the sequence homology that TpP 31 is a structural component of the vacuolar H+-ATPase.  相似文献   
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Light and electron microscopical studies on the effect of a culture filtrate of Erwina herbicola B 247 and herbicolin A on Fusarium culmorum The effect of a culture filtrate of Erwinia herbicola B 247 and the antibiotic herbicolin A, respectively, on the hyphae of Fusarium culmorum was studied in vitro using light and electron microscopy. The light microscopy revealed a swelling and disruption of the hyphae tips with a release of cytoplasm. Ultrastructural investigations demonstrated the appearance of electron-dense material of a round or tubular structure in the cell wall. On its inner side, an accumulation of electron-dense material formed a spongy structure associated with the altered plasma membrane. Finally, a complete dissolution of the cell wall was observed.  相似文献   
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