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81.
82.
Isabella Santi Alfredo Pezzicoli Mattia Bosello Francesco Berti Massimo Mariani John L. Telford Guido Grandi Marco Soriani 《PloS one》2008,3(11)
Streptococcal pullulanases have been recently proposed as key components of the metabolic machinery involved in bacterial adaptation to host niches. By sequence analysis of the Group B Streptococcus (GBS) genome we found a novel putative surface exposed protein with pullulanase activity. We named such a protein SAP. The sap gene is highly conserved among GBS strains and homologous genes, such as PulA and SpuA, have been described in other pathogenic streptococci. The SAP protein contains two N-terminal carbohydrate-binding motifs, followed by a catalytic domain and a C-terminal LPXTG cell wall-anchoring domain. In vitro analysis revealed that the recombinant form of SAP is able to degrade α-glucan polysaccharides, such as pullulan, glycogen and starch. Moreover, NMR analysis showed that SAP acts as a type I pullulanase. Studies performed on whole bacteria indicated that the presence of α-glucan polysaccharides in culture medium up-regulated the expression of SAP on bacterial surface as confirmed by FACS analysis and confocal imaging. Deletion of the sap gene resulted in a reduced capacity of bacteria to grow in medium containing pullulan or glycogen, but not glucose or maltose, confirming the pivotal role of SAP in GBS metabolism of α-glucans. As reported for other streptococcal pullulanases, we found specific anti-SAP antibodies in human sera from healthy volunteers. Investigation of the functional role of anti-SAP antibodies revealed that incubation of GBS in the presence of sera from animals immunized with SAP reduced the capacity of the bacterium to degrade pullulan. Of interest, anti-SAP sera, although to a lower extent, also inhibited Group A Streptococcus pullulanase activity. These data open new perspectives on the possibility to use SAP as a potential vaccine component inducing functional cross-reacting antibodies interfering with streptococcal infections. 相似文献
83.
Uptake and recycling of pro-BDNF for transmitter-induced secretion by cortical astrocytes 总被引:2,自引:0,他引:2 下载免费PDF全文
Bergami M Santi S Formaggio E Cagnoli C Verderio C Blum R Berninger B Matteoli M Canossa M 《The Journal of cell biology》2008,183(2):213-221
Activity-dependent secretion of brain-derived neurotrophic factor (BDNF) is thought to enhance synaptic plasticity, but the mechanisms controlling extracellular availability and clearance of secreted BDNF are poorly understood. We show that BDNF is secreted in its precursor form (pro-BDNF) and is then cleared from the extracellular space through rapid uptake by nearby astrocytes after θ-burst stimulation in layer II/III of cortical slices, a paradigm resulting in long-term potentiation of synaptic transmission. Internalization of pro-BDNF occurs via the formation of a complex with the pan-neurotrophin receptor p75 and subsequent clathrin-dependent endocytosis. Fluorescence-tagged pro-BDNF and real-time total internal reflection fluorescence microscopy in cultured astrocytes is used to monitor single endocytic vesicles in response to the neurotransmitter glutamate. We find that endocytosed pro-BDNF is routed into a fast recycling pathway for subsequent soluble NSF attachment protein receptor–dependent secretion. Thus, astrocytes contain an endocytic compartment competent for pro-BDNF recycling, suggesting a specialized form of bidirectional communication between neurons and glia. 相似文献
84.
Casadio R Santi V Mirici-Cappa F Magini G Cacciari M Bernardi M Trevisani F 《Hormone research》2008,69(3):189-192
Acquired nevoid telangiectasia (ANT) is observed in several conditions including primary cutaneous disorders, systemic autoimmune disease and hyperestrogenism occurring in puberty, pregnancy and chronic liver disease. We describe a patient in whom ANT was a presenting sign of autoimmune hyperthyroidism, which improved after thyroidectomy. A 43-year-old Caucasian woman experienced an asymptomatic development of multiple widespread red skin lesions, diagnosed to be ANT. Blood tests revealed increased serum levels of free tri-iodothyronine and thyroxine and suppressed thyroid-stimulating hormone. Other causes of ANT were excluded. ANT improved but did not disappear after thyroidectomy. The possible pathogenetic factors linking ANT and Graves' disease, such as an immune-mediated process, altered estrogen metabolism or vasodilatation associated with hyperdynamic circulation, are discussed. 相似文献
85.
Cipollini E Riccio M Di Giaimo R Dal Piaz F Pulice G Catania S Caldarelli I Dembic M Santi S Melli M 《Biochimica et biophysica acta》2008,1783(2):312-322
Progressive myoclonus epilepsy type 1 (EPM1) is a neurodegenerative disease correlating with mutations of the cystatin B gene. Cystatin B is described as a monomeric protein with antiprotease function. This work shows that, in vivo, cystatin B has a polymeric structure, highly resistant to SDS, urea, boiling and sensitive to reducing agents and alkaline pH. Hydrogen peroxide increases the polymeric structure of the protein. Mass spectrometry analysis shows that the only component of the polymers is cystatin B. EPM1 mutants of cystatin B transfected in cultured cells are also polymeric. The banding pattern generated by a cysteine-minus mutant is different from that of the wild-type protein as it contains only monomers, dimers and some very high MW bands while misses components of MW intermediate between 25 and 250 kDa. Overexpression of wild-type or EPM1 mutants of cystatin B in neuroblastoma cells generates cytoplasmic aggregates. The cysteine-minus mutant is less prone to the formation of inclusion bodies. We conclude that cystatin B in vivo has a polymeric structure sensitive to the redox environment and that overexpression of the protein generates aggregates. This work describes a protein with a physiological role characterized by highly stable polymers prone to aggregate formation in vivo. 相似文献
86.
Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes 总被引:7,自引:0,他引:7
Pablo Morales Martin T. Sykes I. Colin Prentice† Pete Smith‡ Benjamin Smith Harald Bugmann§ Bärbel Zierl§ Pierre Friedlingstein¶ Nicolas Viovy¶ Santi Sabaté Anabel Sánchez Eduard Pla Carlos A. Gracia Stephen Sitch†† Almut Arneth Jerome Ogee¶ 《Global Change Biology》2005,11(12):2211-2233
Process‐based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models – RHESSys, GOTILWA+, LPJ‐GUESS and ORCHIDEE – representing both modelling approaches were compared and evaluated against benchmarks provided by eddy‐covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model‐measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA+ performed better in simulating carbon fluxes while LPJ‐GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (Rh). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes. 相似文献
87.
88.
Alejandra Lazzaro Montserrat Corominas Cristina Martí Cristina Flors Laura R Izquierdo Teresa A Grillo Javier G Luis Santi Nonell 《Photochemical & photobiological sciences》2004,3(7):706-710
The light-induced singlet oxygen production and antifungal activity of phenylphenalenone phytoalexins isolated from infected banana plants (Musa acuminata) are reported. Upon absorption of light energy all studied phenylphenalenones sensitise the production of singlet oxygen in polar and non-polar media. Antifungal activity of these compounds towards Fusarium oxysporum is enhanced in the presence of light. These results, together with the correlation of IC50 values under illumination with the quantum yield of singlet oxygen production and the enhancing effect of D2O on the antifungal activity, suggest the intermediacy of singlet oxygen produced by electronic excitation of the phenylphenalenone phytoalexins. 相似文献
89.
In this paper we discuss the possibility of utilizing not only the qualitative component of the information obtained from long-term and short-term tests (as is customary), but also the quantitative component of the results. We suggest that there is probably a precise mathematical relationship between the qualitative and quantitative approaches. We show that utilizing the quantitative approach, it is possible to give confidence limits to a given prediction, a possibility potentially very useful for risk evaluation. We show that starting from a reasonable working hypothesis, it is possible to include even negative data in a unified quantitative approach. Incorporating the quantitative component of the information could offer appreciable gains in predictivity, especially when utilizing batteries of tests. 相似文献
90.