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51.
Neisseria meningitidis is a human pathogen that causes septicemia and meningitis with high mortality. The disease progression is rapid and much remains unknown about the disease process. The understanding of disease development is crucial for development of novel therapeutic strategies and vaccines against meningococcal disease. The use of bioluminescent imaging combined with a mouse disease model allowed us to investigate the progression of meningococcal sepsis over time. Injection of bacteria in blood demonstrated waves of bacterial clearance and growth, which selected for Opa-expressing bacteria, indicating the importance of this bacterial protein. Further, N. meningitidis accumulated in the thyroid gland, while thyroid hormone T4 levels decreased. Bacteria reached the mucosal surfaces of the upper respiratory tract, which required expression of the meningococcal PilC1 adhesin. Surprisingly, PilC1 was dispensable for meningococcal growth in blood and for crossing of the blood-brain barrier, indicating that the major role of PilC1 is to interact with mucosal surfaces. This in vivo study reveals disease dynamics and organ targeting during meningococcal disease and presents a potent tool for further investigations of meningococcal pathogenesis and vaccines in vivo. This might lead to development of new strategies to improve the outcome of meningococcal disease in human patients. 相似文献
52.
Life grows almost everywhere on earth, including in extreme environments and under harsh conditions. Organisms adapted to high temperatures are called thermophiles (growth temperature 45-75 degrees C) and hyperthermophiles (growth temperature >or= 80 degrees C). Proteins from such organisms usually show extreme thermal stability, despite having folded structures very similar to their mesostable counterparts. Here, we summarize the current data on thermodynamic and kinetic folding/unfolding behaviors of proteins from hyperthermophilic microorganisms. In contrast to thermostable proteins, rather few (i.e. less than 20) hyperthermostable proteins have been thoroughly characterized in terms of their in vitro folding processes and their thermodynamic stability profiles. Examples that will be discussed include co-chaperonin proteins, iron-sulfur-cluster proteins, and DNA-binding proteins from hyperthermophilic bacteria (i.e. Aquifex and Theromotoga) and archea (e.g. Pyrococcus, Thermococcus, Methanothermus and Sulfolobus). Despite the small set of studied systems, it is clear that super-slow protein unfolding is a dominant strategy to allow these proteins to function at extreme temperatures. 相似文献
53.
Per Heydorn Olle Anderbrant Lars J. Jonsson Glenn P. Svensson 《Journal of Applied Entomology》2019,143(10):1193-1195
The pest Plodia interpunctella (Hübner) is reared in many research laboratories. In a culture established in 1996, attraction of males to the female‐produced sex pheromone in flight tunnel assays gradually decreased after ≈15 years of rearing. A new culture was established to enable comparison with the old culture regarding traits associated with mate finding. Female calling activity, pheromone titre and male antennal response to pheromone components did not differ between cultures. In contrast, very few males from the old culture reached the pheromone source in flight tunnel assays compared with 61%–81% of males from the other culture. Our results highlight the importance of maintaining viable insect cultures for research purposes and suggest frequent evaluation of traits involved in chemical communication in such cultures to ensure reliable results in experiments. 相似文献
54.
Using stochastic simulations and elasticity analysis, we show that there are inherent differences in the risk of extinction between life histories with different demographies. Which life history is the most vulnerable depends on which vital rate varies. When juvenile survival varies semelparous organisms with delayed reproduction are the most vulnerable ones, while a varying developmental rate puts a greater threat to semelparous organisms with rapid development. Iteroparous organisms are the most vulnerable ones when adult survival varies. Generally, we do not expect to observe organisms in nature having variation in vital rates that produce a high risk of extinction. Given the results here we therefore predict that iteroparous organisms should show low variation in adult survival. Moreover, we predict that semelparous organisms should show low variation in juvenile survival and low variation in developmental rate. The effect of temporal correlation on extinction risk is most pronounced in organisms with semelparous life histories. 相似文献
55.
Severson W Partin L Schmaljohn CS Jonsson CB 《The Journal of biological chemistry》1999,274(47):33732-33739
The nucleocapsid (N) protein functions in hantavirus replication through its interactions with the viral genomic and antigenomic RNAs. To address the biological functions of the N protein, it was critical to first define this binding interaction. The dissociation constant, K(d), for the interaction of the Hantaan virus (HTNV) N protein and its genomic S segment (vRNA) was measured under several solution conditions. Overall, increasing the NaCl and Mg(2+) in these binding reactions had little impact on the K(d). However, the HTNV N protein showed an enhanced specificity for HTNV vRNA as compared with the S segment open reading frame RNA or a nonviral RNA with increasing ionic strength and the presence of Mg(2+). In contrast, the assembly of Sin Nombre virus N protein-HTNV vRNA complexes was inhibited by the presence of Mg(2+) or an increase in the ionic strength. The K(d) values for HTNV and Sin Nombre virus N proteins were nearly identical for the S segment open reading frame RNA, showing weak affinity over several binding reaction conditions. Our data suggest a model in which specific recognition of the HTNV vRNA by the HTNV N protein resides in the noncoding regions of the HTNV vRNA. 相似文献
56.
57.
Microbiological characterization of wet wheat distillers' grain, with focus on isolation of lactobacilli with potential as probiotics 总被引:4,自引:0,他引:4
Pedersen C Jonsson H Lindberg JE Roos S 《Applied and environmental microbiology》2004,70(3):1522-1527
Wet wheat distillers' grain (WWDG), a residue from ethanol fermentation, was examined from a microbiological perspective. After storage, WWDG was characterized by a high content of lactobacilli, nondetectable levels of other bacteria, occasional occurrence of yeasts, and a pH of about 3.6 and contained a mixture of lactic acid, acetic acid, and ethanol. The composition of lactobacilli in WWDG was simple, including primarily the species Lactobacillus amylolyticus, Lactobacillus panis, and Lactobacillus pontis, as determined by 16S rRNA gene sequencing. Since the use of WWDG as pig feed has indicated a health-promoting function, some relevant characteristics of three strains of each of these species were examined together with basal physiological parameters, such as carbohydrate utilization and growth temperature. Seven of the strains were isolated from WWDG, and two strains from pig feces were included for comparison. It was clear that all three species could grow at temperatures of 45 to 50 degrees C, with L. amylolyticus being able to grow at temperatures as high as 54 degrees C. This finding could be the explanation for the simple microflora of WWDG, where a low pH together with a high temperature during storage would select for these organisms. Some strains of L. panis and L. pontis showed prolonged survival at pH 2.5 in synthetic stomach juice and good growth in the presence of porcine bile salt. In addition, members of all three species were able to bind to immobilized mucus material in vitro. Especially the isolates from pig feces but, interestingly, some isolates from WWDG as well possessed properties that might be of importance for colonization of the gastrointestinal tracts of pigs. 相似文献
58.
Zhang H Berg JS Li Z Wang Y Lång P Sousa AD Bhaskar A Cheney RE Strömblad S 《Nature cell biology》2004,6(6):523-531
Unconventional myosins are actin-based motors with a growing number of attributed functions. Interestingly, it has been proposed that integrins are transported by unidentified myosins to facilitate cellular remodelling. Here we present an interaction between the unconventional myosin-X (Myo10) FERM (band 4.1/ezrin/radixin/moesin) domain and an NPXY motif within beta-integrin cytoplasmic domains. Importantly, knock-down of Myo10 by short interfering RNA impaired integrin function in cell adhesion, whereas overexpression of Myo10 stimulated the formation and elongation of filopodia in an integrin-dependent manner and relocalized integrins together with Myo10 to the tips of filopodia. This integrin relocalization and filopodia elongation did not occur with Myo10 mutants deficient in integrin binding or with a beta(1)-integrin point mutant deficient in Myo10 binding. Taken together, these results indicate that Myo10-mediated relocalization of integrins might serve to form adhesive structures and thereby promote filopodial extension. 相似文献
59.
Waters S Fae A Gondalia J Holm J Karlström L Nilsson U Jonsson O 《Free radical research》2004,38(3):283-293
Objective: Free radicals contribute to the tissue damage caused by ischaemia-reperfusion. The aim of the present study was to investigate whether preoperative antioxidant therapy (allopurinol) affects free radical levels in cerebral venous blood in connection with surgery for carotid artery stenosis.
Materials and methods: Twenty-five patients were randomised into the study. Thirteen were controls and 12 were pretreated with allopurinol the day before surgery. Before, during and after surgery, blood samples were drawn from the ipsilateral jugular vein. Radical levels were measured using the spin trap technique ex vivo using OXANOH as the spin trap. Multivariate statistics were used with Principal Component Analysis and Partial Least Square regression analysis.
Results: Radical levels increased with diabetes, high leukocyte count, high creatinine and a high degree of contralateral stenosis. Radical levels decreased with high age, blood pressure, collateral circulation as well as operation for left-side carotid artery stenosis. After pretreatment with allopurinol, several of the relationships noted in the control group were eliminated, i.e. leukocyte count, side of operation, Betapred pretreatment and collateral circulation.
Conclusions: Radical levels can be determined in connection with surgery for carotid artery stenosis using an ex vivo spin trap method. With preoperative antioxidant therapy the relationships between enhanced radical levels and clinical data, as seen in control subjects, disappeared. This might indicate a beneficial effect of preoperative pretreatment with antioxidants. 相似文献
Materials and methods: Twenty-five patients were randomised into the study. Thirteen were controls and 12 were pretreated with allopurinol the day before surgery. Before, during and after surgery, blood samples were drawn from the ipsilateral jugular vein. Radical levels were measured using the spin trap technique ex vivo using OXANOH as the spin trap. Multivariate statistics were used with Principal Component Analysis and Partial Least Square regression analysis.
Results: Radical levels increased with diabetes, high leukocyte count, high creatinine and a high degree of contralateral stenosis. Radical levels decreased with high age, blood pressure, collateral circulation as well as operation for left-side carotid artery stenosis. After pretreatment with allopurinol, several of the relationships noted in the control group were eliminated, i.e. leukocyte count, side of operation, Betapred pretreatment and collateral circulation.
Conclusions: Radical levels can be determined in connection with surgery for carotid artery stenosis using an ex vivo spin trap method. With preoperative antioxidant therapy the relationships between enhanced radical levels and clinical data, as seen in control subjects, disappeared. This might indicate a beneficial effect of preoperative pretreatment with antioxidants. 相似文献
60.
DNA polymerase epsilon (Pol epsilon) from Saccharomyces cerevisiae consists of four subunits (Pol2, Dpb2, Dpb3, and Dpb4) and is essential for chromosomal DNA replication. Biochemical characterizations of Pol epsilon have been cumbersome due to protease sensitivity and the limited amounts of Pol epsilon in cells. We have developed a protocol for overexpression and purification of Pol epsilon from S. cerevisiae. The native four-subunit complex was purified to homogeneity by conventional chromatography. Pol epsilon was characterized biochemically by sedimentation velocity experiments and gel filtration experiments. The stoichiometry of the four subunits was estimated to be 1:1:1:1 from colloidal Coomassie-stained gels. Based on the sedimentation coefficient (11.9 S) and the Stokes radius (74.5 A), a molecular mass for Pol epsilon of 371 kDa was calculated, in good agreement with the calculated molecular mass of 379 kDa for a heterotetramer. Furthermore, analytical equilibrium ultracentrifugation experiments support the proposed heterotetrameric structure of Pol epsilon. Thus, both DNA polymerase delta and Pol epsilon are purified as monomeric complexes, in agreement with accumulating evidence that Pol delta and Pol epsilon are located on opposite strands of the eukaryotic replication fork. 相似文献