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排序方式: 共有172条查询结果,搜索用时 15 毫秒
51.
Boyen F Pasmans F Van Immerseel F Morgan E Botteldoorn N Heyndrickx M Volf J Favoreel H Hernalsteens JP Ducatelle R Haesebrouck F 《Veterinary microbiology》2008,128(3-4):364-373
Virulence genes regulated by the SsrA/B system are indispensable for systemic disease in BALB/c mice. The role of this regulating system in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. In the present study, the interactions of Salmonella Typhimurium and an ssrA/B mutant were compared in vitro and in vivo. The ssrA/B mutant strain displayed decreased Salmonella Pathogenicity Island 2 (SPI-2) expression levels, showed a replication defect in mouse macrophages and was attenuated in a mouse model after oral inoculation. Using real time qRT-PCR and a porcine ileal loop model, it was shown that the ssrA/B mutant strain was not significantly attenuated in overall virulence and SPI-1 expression in specific. Flowcytometric analysis demonstrated that the ssrA/B mutant strain was defective in intracellular replication in porcine macrophages. After oral inoculation of piglets with the wild type strain or the ssrA/B mutant strain, the animals of both groups excreted Salmonella and were colonized by Salmonella to the same extent. In an intravenous mixed infection model, the ssrA/B mutant strain was defective in the colonization of several internal organs. These results suggest that the ssrA/B gene of Salmonella Typhimurium plays a limited role in the persistent intestinal colonization of pigs. 相似文献
52.
Van Deun K Pasmans F Ducatelle R Flahou B Vissenberg K Martel A Van den Broeck W Van Immerseel F Haesebrouck F 《Veterinary microbiology》2008,130(3-4):285-297
Although poultry meat is now recognized as the main source of Campylobacter jejuni gastroenteritis, little is known about the strategy used by the bacterium to colonize the chicken intestinal tract. In this study, the mechanism of C. jejuni colonization in chickens was studied using four human and four poultry isolates of C. jejuni. The C. jejuni strains were able to invade chicken primary cecal epithelial crypt cells in a predominantly microtubule-dependent way (five out of eight strains). Invasion of cecal epithelial cells was not accompanied by necrosis or apoptosis in the cell cultures, nor by intestinal inflammation in a cecal loop model. C. jejuni from human origin displayed a similar invasive profile compared to the poultry isolates. Invasiveness of the strains in vitro correlated with the magnitude of spleen colonization in C. jejuni inoculated chicks. The C. jejuni bacteria that invaded the epithelial cells were not able to proliferate intracellularly, but quickly evaded from the cells. In contrast, the C. jejuni strains were capable of replication in chicken intestinal mucus. These findings suggest a novel colonization mechanism by escaping rapid mucosal clearance through short-term epithelial invasion and evasion, combined with fast replication in the mucus. 相似文献
53.
Humic acids (HA) extracted from Chernozem (Haplic Phaeozem), Brown Earth (Cambic Umbrisol) and Podzol (Humic Podzol) were added as a supplemental source of nutrients, or as the sole sources of carbon and nitrogen to aerobic cultures of complex microbial communities indigenous to the same individual soils. Depending on nutrient conditions in the individual cultures and origin of HA, between 14 and 86 % of the added HA was utilized. The formation of microbial biomass was enhanced up to six fold in the full-strength nutrient media supplemented with humic acids but was strongly inhibited if HA served as the sole C source. HA preparations re-isolated from the microbial cultures exhibited elemental and structural changes characteristic for early diagenetic transformations of humic substances. These included an increase in carbon content, C:N ratio, infra-red absorption typical for aromatics, and a decrease in infra-red absorption associated with aliphatic acids, nitrogenous and carbohydrate-like substances. 相似文献
54.
Gazdik Filip Penazova Eliska Cechova Jana Baranek Miroslav Eichmeier Ales 《植物病害和植物保护杂志》2019,126(6):517-528
Journal of Plant Diseases and Protection - Pseudomonas amygdali pv. lachrymans (Pal) is a bacterium that causes angular leaf spot disease of cucumbers. There is no direct protection against this... 相似文献
55.
Scope A Schwendenwein I Enders F Gabler C Seidl E Filip T Soklaridis U 《Avian diseases》2000,44(4):885-890
We established reference ranges for three hematologic and 15 clinical chemistry parameters of 40 clinically healthy birds of the genus Eos. The following species were included to the study: Eos histrio (n = 19), Eos squamata (n = 8), Eos bomea (n = 5), Eos reticulata (n = 4), Eos cyanogenia (n = 4). Detailed information concerning methodology, which is often missing in papers dealing with reference values, is included. As far as possible, data are compared with literature, and some thoughts on obvious deviations are given. The problem of establishing reference values in rare species is reviewed. 相似文献
56.
Besides enzymatic inactivation, catecholamines bind non-enzymatically and irreversible to proteins. The physiological impact of these catecholamine adducts is still unclear. We therefore collected basic data about the distribution of catecholamine adducts in the rat after repeated intravenous administration of 3H-adrenaline and 3H-noradrenaline. 相似文献
57.
Leen Timbermont Lina De Smet Filip Van Nieuwerburgh Valeria R Parreira Gonzalez Van Driessche Freddy Haesebrouck Richard Ducatelle John Prescott Dieter Deforce Bart Devreese Filip Van Immerseel 《Veterinary research》2014,45(1):40
Necrotic enteritis in broiler chickens is associated with netB positive Clostridium perfringens type A strains. It is known that C. perfringens strains isolated from outbreaks of necrotic enteritis are more capable of secreting factors inhibiting growth of other C. perfringens strains than strains isolated from the gut of healthy chickens. This characteristic could lead to extensive and selective presence of a strain that contains the genetic make-up enabling to secrete toxins that cause gut lesions. This report describes the discovery, purification, characterization and recombinant expression of a novel bacteriocin, referred to as perfrin, produced by a necrotic enteritis-associated netB-positive C. perfringens strain. Perfrin is a 11.5 kDa C-terminal fragment of a 22.9 kDa protein and showed no sequence homology to any currently known bacteriocin. The 11.5 kDa fragment can be cloned into Escherichia coli, and expression yielded an active peptide. PCR detection of the gene showed its presence in 10 netB-positive C. perfringens strains of broiler origin, and not in other C. perfringens strains tested (isolated from broilers, cattle, sheep, pigs, and humans). Perfrin and NetB are not located on the same genetic element since NetB is plasmid-encoded and perfrin is not. The bacteriocin has bactericidal activity over a wide pH-range but is thermolabile and sensitive to proteolytic digestion (trypsin, proteinase K). C. perfringens bacteriocins, such as perfrin, can be considered as an additional factor involved in the pathogenesis of necrotic enteritis in broilers. 相似文献
58.
Christin Selige Monike Quirino Filip Schröter Matteo Aepli Martin Schulze 《Reproduction in domestic animals》2021,56(8):1152-1155
Egg yolk (EY, control) is an essential ingredient of diluents for boar semen cryopreservation. Pasteurized egg yolk (PEY) reduces hygienic risks in processing and is easier to standardize. The aim of this study was to evaluate the in vitro effect of PEY (treatment) on frozen-thawed boar semen. In a split-sample approach (n = 13 boars), it could be shown that there is neither an influence (p > .05) on post-thawing motility (PTM: 5, 30 and 120 min) nor on morphologically intact sperm, percentage of acrosome defects and membrane fluidity using a PEY extender compared to the control. Mitochondrial activity (p = .043), membrane integrity (p = .015) and PTM 300 min (p = .023) were slightly affected in the treatment group. Overall, sperm quality was at a high level in both experimental groups. Further studies are needed to determine the impact of PEY on the fertilizing capacity of boar ejaculates. 相似文献
59.
Filip Moldan Richard A. Skeffington Carl-Magnus Mörth Peter Torssander Hans Hultberg John Munthe 《Water, air, and soil pollution》2004,154(1-4):371-384
The Covered Catchment Experiment at Gårdsjön is a large scale forest ecosystem manipulation, where acid precipitation was intercepted by a 7000 m2 plastic roof and replaced by `clean precipitation' sprinkled below the roof for ten years between 1991 and 2001. The treatment resulted in a strong positive response of runoff quality. The runoff sulphate, inorganic aluminium and base cations decreased, while there was a strong increase in runoff ANC and a moderate increase in pH. The runoff continued to improve over the whole duration of the experiment. The achieved quality was, however, after ten years still considerably worse than estimated pre-industrial runoff at the site. Stable isotopes of sulphur were analysed to study the soil sulphur cycling. At the initial years of the experiment, the desorption of SO4 from the mineral soil appeared to control the runoff SO4 concentration. However, as the experiment proceeded, there was growing evidence that net mineralisation of soil organic sulphur in the humus layer was an additional source of SO4 in runoff. This might provide a challenge to current acidification models. The experiment convincingly demonstrated on a catchment scale, that reduction in acid deposition causes an immediate improvement of surface water quality even at heavily acidified sites. The improvement of the runoff appeared to be largely a result of cation exchange processes in the soil due to decreasing concentrations of the soil solution, while any potential change in soil base saturation seemed to be less important for the runoff chemistry over the short time period of one decade. These findings should be considered when interpreting and extrapolating regional trends in surface water chemistry to the terrestrial parts of ecosystems. 相似文献
60.
ABSTRACT: Polymerase chain reaction (PCR) restriction fragment length polymorphism analysis of mitochondrial DNA was applied to the genetic structure and evolutionary history of the more ancestral Pangasianodon hypophthalmus ( n = 82), and the recently speciated catfish Pangasius bocourti ( n = 90) from the Cambodian Mekong River. Both pangasiids were characterized by a lack of genetic population structure that may result from high levels of contemporary gene flow. Genetic diversity was lower in P. hypophthalmus than in P. bocourti . However, a different evolutionary history was inferred for both species based on genealogical and demographic analyses (mismatch analysis, Tajima's D- and Fu's F S -tests). The genetic profile of the more ancestral P. hypophthalmus shows indications of a recent population bottleneck, whereas the recently speciated P. bocourti shows signatures of historical population expansion. This study stresses the importance of preserving the migration routes in the Cambodian Mekong basin in order to maintain the genetic diversity and long-term integrity of both species. 相似文献