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61.
The LexA regulated SOS network is a bacterial response to DNA damage of metabolic or environmental origin. In Clostridium difficile, a nosocomial pathogen causing a range of intestinal diseases, the in-silico deduced LexA network included the core SOS genes involved in the DNA repair and genes involved in various other biological functions that vary among different ribotypes. Here we describe the construction and characterization of a lexA ClosTron mutant in C. difficile strain. The mutation of lexA caused inhibition of cell division resulting in a filamentous phenotype. The lexA mutant also showed decreased sporulation, a reduction in swimming motility, greater sensitivity to metronidazole, and increased biofilm formation. Changes in the regulation of toxin A, but not toxin B, were observed in the lexA mutant in the presence of sub-inhibitory concentrations of levofloxacin. C. difficile LexA is, therefore, not only a regulator of DNA damage but also controls many biological functions associated with virulence. R20291相似文献
62.
Annual killifish of the genus Nothobranchius often co-occur in temporary savannah pools. Their space- and time-limited environment does not allow for any substantial habitat or temporal segregation. Coexisting species are therefore predicted to have well separated trophic niches to avoid intense food competition. Although in a previous “snapshot” study using stomach content analysis (SCA), the trophic niches of three sympatric species (N. furzeri, N. orthonotus, and N. pienaari) were found to vary among species, the difference was relatively weak and inconsistent across different sites. Here, we used the time-integrative capacity of stable isotope analysis to test whether the trophic niches of sympatric Mozambican Nothobranchius are more distinct over a long-term period. Analysis of carbon and nitrogen stable isotopes separated the trophic niche and trophic position of N. pienaari but failed to find any difference between N. furzeri/N. kadleci and N. orthonotus. No segregation was found at the sites with low prey diversity. In contrast, SCA identified N. orthonotus as the species with the most distinct trophic niche. We discuss the effect of prey diversity and different sensitivities of stomach content and stable isotope analysis in general and conclude that the trophic niches of the three sympatric Nothobranchius species are well separated. 相似文献
63.
CDC traps were used to determine the maximum radius of carbon dioxide attraction within forest habitat (a forest plant community with Carpino betuli-Quercetum roburis). A central CDC trap with dry ice (CO2) was set as the source of attractant (Ck). Around Ck trap two circles (A and B) of CDC traps without attractants were placed. Circle A was constituted of 6 CDC traps and Circles B with 12 CDC traps. Radius from Circle A and B to the Ck trap were used to determine CO2 maximum range. During the experiment, the average emissions of CO2 were 0.08 to 0.1 g s?1. Regarding the data, optimal radius attraction where CO2 was affected on mosquitoes was between 55 and 70 m from the source. Results propose that the distance between traps should be greater than 140 m, to ensure the absence of bias by each of the traps. Changes in CO2 maximum concentration and wind velocity directly affected the catch of different species. The number of Ochlerotatus sticticus collected was positively correlated with wind speed. 相似文献
64.
This study examined whether gate setup and turn radii influence energy dissipation in slalom skiing. 3D kinematical measurements were performed over two runs on the same slope in a WC slalom competition with two different gate setups: 1) open gates (OG) and 2) open gates with a delayed gate (DG). Using the arithmetic mean of the skis' turn radii (R(AMS)) the slalom turns were divided into 1) initiation phase (R(AMS) > 15 m) and steering phase (R(AMS) < 15 m). The results show differences between OG and DG regarding: 1) the absolute center of gravity's (CG) velocity, 2) absolute acceleration, 3) CG turn radii and R(AMS), 4) ground reaction forces (F) and 5) energy dissipation during skiing (all p < .05). In both gate setups the highest F and the highest energy dissipation were present in the steering phase, whereas the correlation between R(AMS) and energy dissipation was low (OG: r = .364 and DG: r = .214, both p < .001). In summary, compared with plain open gates, an additional delayed gate prolonged the turn radii and decreased energy dissipation in the beginning of the initiation phase, despite the fact that the relative frequency of occurrence of the highest energy dissipation was higher in DG. 相似文献
65.
Branka Salopek‐Sondi Jasenka Piljac‐Žegarac Volker Magnus Nevenka Kopjar 《Journal of biochemical and molecular toxicology》2010,24(3):165-173
Auxins, of which indole‐3‐acetic acid (IAA) is the most widespread representative, are plant hormones. In addition to plants, IAA also naturally occurs in humans in micromolar concentrations. In the presence of peroxidase, indolic auxins are converted to cytotoxic oxidation products and have thus been proposed for use in gene‐directed enzyme/prodrug tumor therapy. Since data on the genotoxicity of IAA and its derivatives are not consistent, here we investigate the early DNA damaging effects (2‐h treatment) of the auxins, IAA, and 2‐methyl‐indole‐3‐acetic acid (2‐Me‐IAA) by the alkaline comet assay and compare them with their free radical–scavenging activity measured by the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. Human neutrophils are chosen as the test system since they possess inherent peroxidase activity. The results of the comet assay indicate an increase in DNA damage in a dose‐dependent manner up to 1.00 mM of both auxins. Generally, IAA applied in the same concentration had greater potential to damage DNA in human neutrophils than did 2‐Me‐IAA. The genotoxicities of the two examined auxins are negatively correlated with their antioxidant activities, as measured by the DPPH assay; 2‐Me‐IAA showed a higher antioxidant capacity than did IAA. We assume that differences in the molecular structure of the tested auxins contributed to differences in their metabolism, in particular, with respect to interactions with peroxidases and other oxidative enzymes in neutrophils. However, the exact mechanisms have to be elucidated in future studies. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:165–173, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20323 相似文献
66.
Markéta Ondračková Kateřina Francová Martina Dávidová Matej Polačik Pavel Jurajda 《Ecological Research》2010,25(4):857-866
The success of introduced species is often facilitated by escape from the effects of natural predators and parasites. Introduced species can profit from this favourable situation, attaining higher population densities and greater individual sizes in novel areas. In this study, somatic condition and parasite infection were compared between native and non-native populations of Neogobius kessleri Günther; introduced only within the interconnected Danube and Rhine River system, and N. melanostomus (Pallas); widely introduced throughout several river systems in Europe and North America. Higher values of Fulton’s condition factor were observed in non-native populations of both goby species. Neogobius melanostomus attained higher gonadosomatic index values in non-native populations, indicating potential increased investment in reproduction in its new area. A lower splenosomatic index was observed in non-native populations, especially in N. melanostomus. Parasite infracommunity richness and mean abundance were higher in N. kessleri in both native and non-native populations, suggesting higher susceptibility of N. kessleri to these parasites. Non-native populations of both hosts showed higher infra-community richness as a result of acquiring parasites native to the new area, but lower parasite abundance. Differences in success of the introduction and establishment in new areas between the two fish species may be associated with a relatively low parasite infection rate and a higher gonadosomatic index in non-native populations of N. melanostomus in comparison to N. kessleri. 相似文献
67.
Karel Královec Zbyněk Roček Pavla Žáková Vladimíra Mužáková 《Journal of morphology》2010,271(9):1078-1093
We use histological techniques and computer‐aided three‐dimensional reconstructions made from serial histological sections to describe the ontogeny of the ethmoidal endocranium of discoglossid frog Discoglossus pictus. We identify a pattern of development for the suprarostral cartilage that differs from previous findings and probably represents the ancestral anuran pattern. The nasal cartilages, including the inferior prenasal cartilage, are de novo adult structures. The only larva‐derived structures of the adult nasal capsules are the posterior aspects of the solum nasi and septum nasi. We also identify patterns of development for the ethmoid plate and postnasal wall that occur during early in ontogenesis. These patterns are associated with development events during metamorphic climax. The pattern of timing of chondrification of the anterior nasal cartilages more closely coincides with that of the neobatrachian species than that recorded for the pelobatid frog Spea. In addition, this study supports a sister taxon relationship between Discoglossus and Alytes. J. Morphol. 271:1078‐1093, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
68.
69.
Matej Reberšek Cécile Faurie Maša Kandušer Selma Čorović Justin Teissié Marie-Pierre Rols Damijan Miklavčič 《Biomedical engineering online》2007,6(1):25
Background
Gene electrotransfer is a non-viral method used to transfer genes into living cells by means of high-voltage electric pulses. An exposure of a cell to an adequate amplitude and duration of electric pulses leads to a temporary increase of cell membrane permeability. This phenomenon, termed electroporation or electropermeabilization, allows various otherwise non-permeant molecules, including DNA, to cross the membrane and enter the cell. The aim of our research was to develop and test a new system and protocol that would improve gene electrotransfer by automatic change of electric field direction between electrical pulses. 相似文献70.
Žunić Vladimira Jafari Timea Hajnal Grabić Jasna Đurić Simonida Stamenov Dragana 《Journal of applied phycology》2022,34(2):903-913
Journal of Applied Phycology - Co-cultivation of plants and microalgae represents an optimized production method which is less resource intense and it is ecologically correct and clean.... 相似文献