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221.
Daniel Souto‐Vilarós Ana Vuleta Sanja Manitašević Jovanović Sanja Budečević Hui Wang Yuval Sapir Eric Imbert 《Oikos》2018,127(6):834-846
Plant–pollinator interactions are believed to play a major role in the evolution of floral traits. Flower colour and flower size are important for attracting pollinators, directly influencing reproduction, and thus expected to be under pollinator‐mediated selection. Pollinator‐mediated selection is also proposed to play a role in maintaining flower colour polymorphism within populations. However, pigment concentrations, and thus flower colour, are also under selective pressures independent of pollinators. We quantified phenotypic pollinator‐mediated selection on flower colour and size in two colour polymorphic Iris species. Using female fitness, we estimated phenotypic selection on flower colour and size, and tested for pollinator‐mediated selection by comparing selection gradients between flowers open to natural pollination and supplementary pollinated flowers. In both species, we found evidence for pollen limitation, which set the base for pollinator‐mediated selection. In the colour dimorphic Iris lutescens, while pigment concentration and flower size were found to be under selection, this was independent of pollinators. For the polymorphic Iris pumila, pigment concentration is under selective pressure by pollinators, but only for one colour morph. Our results suggest that pollinators are not the main agents of selection on floral traits in these irises, as opposed to the accepted paradigm on floral evolution. This study provides an opposing example to the largely‐accepted theory that pollinators are the major agent of selection on floral traits. 相似文献
222.
Paula Giselle Czaikoski José Maurício Segundo Correia Mota Daniele Carvalho Nascimento Fabiane S?nego Fernanda Vargas e Silva Castanheira Paulo Henrique Melo Gabriela Trentin Scortegagna Rangel Leal Silva Romualdo Barroso-Sousa Fabrício Oliveira Souto Antonio Pazin-Filho Florencio Figueiredo José Carlos Alves-Filho Fernando Queiróz Cunha 《PloS one》2016,11(2)
Organ dysfunction is a major concern in sepsis pathophysiology and contributes to its high mortality rate. Neutrophil extracellular traps (NETs) have been implicated in endothelial damage and take part in the pathogenesis of organ dysfunction in several conditions. NETs also have an important role in counteracting invading microorganisms during infection. The aim of this study was to evaluate systemic NETs formation, their participation in host bacterial clearance and their contribution to organ dysfunction in sepsis. C57Bl/6 mice were subjected to endotoxic shock or a polymicrobial sepsis model induced by cecal ligation and puncture (CLP). The involvement of cf-DNA/NETs in the physiopathology of sepsis was evaluated through NETs degradation by rhDNase. This treatment was also associated with a broad-spectrum antibiotic treatment (ertapenem) in mice after CLP. CLP or endotoxin administration induced a significant increase in the serum concentrations of NETs. The increase in CLP-induced NETs was sustained over a period of 3 to 24 h after surgery in mice and was not inhibited by the antibiotic treatment. Systemic rhDNase treatment reduced serum NETs and increased the bacterial load in non-antibiotic-treated septic mice. rhDNase plus antibiotics attenuated sepsis-induced organ damage and improved the survival rate. The correlation between the presence of NETs in peripheral blood and organ dysfunction was evaluated in 31 septic patients. Higher cf-DNA concentrations were detected in septic patients in comparison with healthy controls, and levels were correlated with sepsis severity and organ dysfunction. In conclusion, cf-DNA/NETs are formed during sepsis and are associated with sepsis severity. In the experimental setting, the degradation of NETs by rhDNase attenuates organ damage only when combined with antibiotics, confirming that NETs take part in sepsis pathogenesis. Altogether, our results suggest that NETs are important for host bacterial control and are relevant actors in the pathogenesis of sepsis. 相似文献
223.
Díaz JF Strobe R Engelborghs Y Souto AA Andreu JM 《The Journal of biological chemistry》2000,275(34):26265-26276
We have determined the kinetic scheme and the reaction rates of binding to microtubules of two fluorescent taxoids, 7-O-[N-(4'-fluoresceincarbonyl)-l-alanyl]Taxol (Flutax-1) and 7-O-[N-(2,7-difluoro-4'-fluoresceincarbonyl)-l-alanyl]Taxol (Flutax-2). Flutax-1 and Flutax-2 bind to microtubules with high affinity (K(a) approximately 10(7) m(-1), 37 degrees C). The binding mechanism consists of a fast bimolecular reaction followed by at least two monomolecular rearrangements, which were characterized with stopped-flow techniques. The kinetic constants of the bimolecular reaction were 6.10 +/- 0.22 x 10(5) m(-1) s(-1) and 13.8 +/- 1.8 x 10(5) m(-1) s(-1) at 37 degrees C, respectively. A second slow binding step has been measured employing the change of fluorescence anisotropy of the probe. The reversal of this reaction is the rate-limiting step of dissociation. A third step has been detected using small angle x-ray scattering and involves a 2-nm increase in the diameter of microtubules. It is suggested that the first step entails the binding of the Taxol moiety and the second a relative immobilization of the fluorescent probe. The equilibrium and some kinetic measurements required the use of stabilized cross-linked microtubules, which preserved taxoid binding. The results indicate that the Taxol binding site is directly accessible, in contrast with its location at lumen in the current model of microtubules. An alternative structural model is considered in which the binding site is located between protofilaments, accessible from the microtubule surface. 相似文献
224.
A fundamental question in the field of artificial neural networks is what set of problems a given class of networks can perform (computability). Such a problem can be made less general, but no less important, by asking what these networks could learn by using a given training procedure (learnability). The basic purpose of this paper is to address the learnability problem. Specifically, it analyses the learnability of sequential RAM-based neural networks. The analytical tools used are those of Automata Theory. In this context, this paper establishes which class of problems and under what conditions such networks, together with their existing learning rules, can learn and generalize. This analysis also yields techniques for both extracting knowledge from and inserting knowledge into the networks. The results presented here, besides helping in a better understanding of the temporal behaviour of sequential RAM-based networks, could also provide useful insights for the integration of the symbolic/connectionist paradigms. 相似文献
225.
226.
A PCR-based method for the screening of bacterial strains with antifungal activity in suppressive soybean rhizosphere 总被引:2,自引:0,他引:2
Giacomodonato Mónica N. Pettinari M. Julia Souto Guadalupe I. Méndez Beatriz S. López Nancy I. 《World journal of microbiology & biotechnology》2001,17(1):51-55
Selection and evaluation of microbial strains for their antifungal activity in natural environments is time- and energy-consuming. We have adapted a PCR-based method to avoid these inconveniences. Soils that are naturally suppressive to plant disease were chosen as a source of antibiotic-producing bacteria. The screening was performed by means of PCR amplification using degenerate primers corresponding to peptide synthetase genes. Amplification fragments were obtained using template DNA from the rhizosphere of three different soybean fields. In order to assay their potential utility in pathogen control, several Bacillus strains were analysed for their in vitro antifungal activity by testing growth inhibition of Sclerotinia sclerotiorum. Four Bacillus sp. isolates gave a positive amplification signal, and three of them had an inhibitory effect on S. sclerotiorum growth, whereas two strains that failed to give an amplification signal did not inhibit fungal growth. These results show that PCR-based techniques could be useful to assess the presence of strains with potential use as biocontrol agents. 相似文献
227.
M Ozkan SG Desai Y Zhang DM Stevenson J Beane EA White ML Guerinot LR Lynd 《Journal of industrial microbiology & biotechnology》2001,27(5):275-280
Characteristics of 13 newly isolated thermophilic, anaerobic, and cellulolytic strains were compared with previously described
strains of Clostridium thermocellum: ATCC 27405 and JW20 (ATCC 31549). Colony morphology, antibiotic sensitivity, fermentation end-products, and cellulose degradation
were documented. All 13 strains were sensitive to erythromycin (5 μg/ml) and chloramphenicol (25 μg/ml), and all strains but
one were sensitive to kanamycin (20 μg/ml). Polymerase chain reaction (PCR) amplification using primers based on gene sequences
from C. thermocellum ATCC 27405 was successful for all 13 strains in the case of the hydrogenase gene and 11 strains in the case of phosphotransacetylase/acetate
kinase genes. Ten strains amplified a product of the expected size with primers developed to be specific for C. thermocellum 16SrRNA primers. Two of the 13 strains did not amplify any product with the PCR primers designed for the phosphotransacetylase/acetate
kinase and 16SrRNA primers. A MboI-like GATC- recognizing restriction activity was present in all of the five strains examined. The results of this study have
several positive implications with respect to future development of a transformation system for cellulolytic thermophiles.
Journal of Industrial Microbiology & Biotechnology (2001) 27, 275–280.
Received 12 September 2000/ Accepted in revised form 20 November 2000 相似文献
228.
Mayra Carraro Di Gregorio Alessandra Vincenzi Jager Pollyana Cristina Maggio Castro Souto Aline Alves Costa George Edwin Rottinghaus Danielle Passarelli Fabio Enrique Lemos Budiño Carlos Humberto Corassin Carlos Augusto Fernandes Oliveira 《Mycotoxin Research》2017,33(2):93-102
In this study, serum aflatoxin B1 (AFB1)-lysine was determined in order to evaluate the in vivo efficacy of a hydrated sodium calcium aluminosilicate (HSCAS) in pigs fed AFB1. Twenty-four 49-day-old crossbred barrows were maintained in individual cages and allowed ad libitum access to feed and water. A completely randomized design was used with six animals assigned to each of four dietary treatments for 21 days as follows: (A) basal diet (BD), (B) BD supplemented with 0.5 % HSCAS, (C) BD supplemented with 1.1 mg/kg AFB1, and (D) BD supplemented with 0.5 % HSCAS and 1.1 mg/kg AFB1. HSCAS was able to alleviate the toxic effects of AFB1 on pigs and reduce (P < 0.05) the levels of serum AFB1-lysine. Cumulative reductions of adduct yield values, calculated through the equation [(pg AFB1-lysine/mg albumin) / (μg AFB1/kg body weight)], were 53.0, 62.8, and 72.1 after 7, 14, and 21 days of oral exposure, respectively. AFB1-lysine has potential as an AFB1-specific biomarker for diagnostic purposes and for evaluating the efficacy of chemoprotective interventions in pigs. 相似文献
229.
Juan Carlos Florez Luciana Souto Mofatto Rejane do Livramento Freitas-Lopes Sávio Siqueira Ferreira Eunize Maciel Zambolim Marcelo Falsarella Carazzolle Laércio Zambolim Eveline Teixeira Caixeta 《Plant molecular biology》2017,93(6):607-621
Transgenic expression of the pepper Bs2 gene confers resistance to Xanthomonas campestris pv. vesicatoria (Xcv) pathogenic strains which contain the avrBs2 avirulence gene in susceptible pepper and tomato varieties. The avrBs2 gene is highly conserved among members of the Xanthomonas genus, and the avrBs2 of Xcv shares 96% homology with the avrBs2 of Xanthomonas citri subsp. citri (Xcc), the causal agent of citrus canker disease. A previous study showed that the transient expression of pepper Bs2 in lemon leaves reduced canker formation and induced plant defence mechanisms. In this work, the effect of the stable expression of Bs2 gene on citrus canker resistance was evaluated in transgenic plants of Citrus sinensis cv. Pineapple. Interestingly, Agrobacterium-mediated transformation of epicotyls was unsuccessful when a constitutive promoter (2× CaMV 35S) was used in the plasmid construction, but seven transgenic lines were obtained with a genetic construction harbouring Bs2 under the control of a pathogen-inducible promoter, from glutathione S-transferase gene from potato. A reduction of disease symptoms of up to 70% was observed in transgenic lines expressing Bs2 with respect to non-transformed control plants. This reduction was directly dependent on the Xcc avrBs2 gene since no effect was observed when a mutant strain of Xcc with a disruption in avrBs2 gene was used for inoculations. Additionally, a canker symptom reduction was correlated with levels of the Bs2 expression in transgenic plants, as assessed by real-time qPCR, and accompanied by the production of reactive oxygen species. These results indicate that the pepper Bs2 resistance gene is also functional in a family other than the Solanaceae, and could be considered for canker control. 相似文献
230.