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- Jansson, D. S., et al.
(författare)
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Brachyspira hyodysenteriae and other strongly beta-haemolytic and indole-positive spirochaetes isolated from mallards (Anas platyrhynchos)
- 2004
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Ingår i: Journal of Medical Microbiology. - : Microbiology Society. - 0022-2615 .- 1473-5644. ; 53:4, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the current study were to collect intestinal spirochaetes (genus Brachyspira) from farmed and wild mallards (Anas platyrhynchos) and to identify and classify those isolates that phenotypically resembled Brachyspira hyodysenteriae, an enteric pathogen of pigs. The isolation rate of Brachyspira spp. was high from both farmed (93%) and wild mallards (78%). In wild mallards, it appeared that Brachyspira spp. were more likely to be found in migratory birds (multivariate analysis: RR = 1(.)8, 95% Cl 1(.)1-3(.)1) than in mallards sampled in a public park. Pure cultures of putative B. hyodysenteriae were obtained from 22 birds. All five isolates from farmed mallards and ten randomly selected isolates with this phenotype were used for further studies. All isolates from farmed mallards and two of the isolates from wild mallards were PCR-positive for the tlyA gene of B. hyodysenteriae. Two isolates from farmed mallards were selected for pulsed field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD) analysis. These isolates clustered with the type and reference strains of B. hyodysenteriae. 16S rDNA sequence analysis performed on 11 of the strains showed that they were all closely related to each other and to the B. hyodysenteriae-Brachyspira intermedia cluster. Three of the mallard isolates had 16S rDNA sequences that were identical to those of B. hyodysenteriae strains R1 and NIV-1 previously isolated from common rheas (Rhea americana). To conclude, the isolates from farmed mallards and two isolates from wild mallards were classified as B. hyodysenteriae based on the factthat they could not be differentiated by any of the applied methods from type, reference and field strains of B. hyodysenteriae. The remaining isolates could not be assigned irrefutably to any of the presently recognized Brachyspira species. These results point to a broader host spectrum of B. hyodysenteriae than is generally recognized, and to the presence in mallards of strongly haemolytic and indole-producing spirochaetes that possess many, but not all, of the currently recognized characteristics of B. hyodysenteriae.
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- Kahnberg, Pia, et al.
(författare)
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The use of a pharmacophore model for identification of novel ligands for the benzodiazepine binding site of the GABA(A) receptor
- 2004
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Ingår i: Journal of Molecular Graphics and Modelling. - : Elsevier BV. - 1093-3263. ; 23:3, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- A Catalyst pharmacophore model has been developed for the benzodiazepine site within the GABA(A) receptor complex. The model is based on a pharmacophore model originally proposed by Cook and co-workers (Drug Des. Discovery 1995, 12, 193-248) and further developed by Kahnberg et al. (J. Med. Chem. 2002,45, 4188-4201). The Catalyst pharmacophore model has been validated by using a series of flavonoids with varying affinities for the benzodiazepine receptor and has then been used as a search query in database searching with the aim of finding novel structures which have the possibility to be modified into novel lead compounds. Five of the hits from the database searching were purchased and their affinities for the benzodiazepine site of the GABA(A) receptor were determined. Two of the compounds displayed K-i values below 10 muM. The substance showing highest potency in-vitro displayed an affinity of 121 nM making it an interesting compound for optimization. The false positive compounds (K-i values > 10 muM affinities) have been analysed in terms of conformational energy penalties and possibilities for hydrogen bond interactions. The analysis clearly demonstrates the need for post processing of Catalyst hits. (C) 2004 Elsevier Inc. All rights reserved.
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- Pettersson, Lage, et al.
(författare)
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17O NMR study of aqueous peroxoisopolymolybdate equilibria at lower peroxide/Mo ratios
- 2003
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; , s. 146-52
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous peroxomolybdates have been studied using 17O NMR together with equilibrium measurements and calculations, over a wide range of conditions. Ten peroxo species are identified, mostly in more than one state of protonation. Some are already known in the solid state, or from equilibrium analysis, but structural information is also obtained for MoO3(HO2)– and the new or previously tentative species Mo2O5(O2)22–, HpMo7O23(O2)2p–6 and HpMo7O23(O2)p–6(p= 0–2). Sites of protonation are identified, as are 17O resonances from both bidentate and monodentate peroxide. Several oxygen exchange processes are also seen, including a probable dimer–tetramer exchange.
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- Pettersson, Mats I., 1960
(författare)
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Contribution to Wideband SAR Space-Time Processing, and Radar Remote Sensing of Sea Ice
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Synthetic Aperture Radar (SAR) has the capability to map the Earth with high resolution and is used in both civilian and military applications. The development of SAR systems is going towards higher resolution. Today there are Wide Band (WB) SAR instruments that have a resolution actually smaller than the operating wavelength. One example is the CARABAS sensor developed by the Swedish Defence Research Establishment (FOA). It operates at VHF and has shown many unique capabilities such as the detection of concealed targets. Great efforts are being made to build WB SAR systems at higher frequencies. One of these projects is the LORA project at FOA. The LORA system will operate on UHF and it will have several antenna channels which can be used for space-time processing, e.g. to suppress clutter and jammers, and to detect ground moving targets. In this thesis we have considered two different areas connected with SAR. In the first part we develop space-time adaptive algorithms for WB SAR systems with array antennas. The aim of the work is to detect ground moving targets and to suppress strong clutter and jammer noise. A likelihood ratio test is proposed for detection. The method combines fast backprojection algorithms with target detection. Moving targets are focused using their proper relative speed. The methodology has been tested on narrow band data. Bistatic antenna effects on WB SAR systems for moving target indication are discussed. Simulations of WB SAR using combined fast backprojection and clutter suppression are presented. Jammer suppression is tested for WB SAR, using space-time adaptive processing. The results are from an experiment with the CARABAS radar. In the second part we examine what a microwave radar sensor actually senses in sea ice and we investigate the capability of the SAR onboard the ERS-1 satellite to classify Arctic sea ice. Polarimetric scatterometer measurements have been carried out at microwave frequencies (L-, S-, C- and X-band). The measurements are compared with scattering models. Conclusions are made of what the radar senses in sea ice, for the different ice types. Sea ice classification methods are tested on ERS-1 SAR images and compared with classifications made by the NASA team algorithm on data from the DMSP satellites Special Scanning Microwave Imager (SSM/I). The results are compared with in situ measurements.
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- Raices, M., et al.
(författare)
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Cellobiose quinone oxidoreductase from the white rot fungus Phanerochaete chrysosporium is produced by intracellular proteolysis of cellobiose dehydrogenase
- 2002
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Ingår i: Biochimica et Biophysica Acta, Gene Structure and Expression. - 0167-4781 .- 1879-2634. ; 1576:02-jan, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- The fungus Phanerochaete chrysosporium was grown in a 10-1 automatic fermenter using cellobiose us carbon source to monitor the induction of cellobiose dehydrogenase (CDH) and cellobiose quinone oxidoreductase (CBQ) enzymes, and to search for tentative cbq and cdh genes and their transcriptional products. After 24 h of induction, CDH was detected in the culture supernatant and a protein was recognized by a specific anti-CDH polyclonal antibody in the sonicated biomass. Northern blot experiments performed with several fungal RNA samples showed, after 24 h of induction. only one single species of an mRNA transcript corresponding in size to the cdh gene (2.5 kb) The relative amount of this transcript decreased as a function of time. Southern blot experiments done with genomic DNA and database search in the recently available genome information also ruled out the presence in this strain of a separate cbq gene distinct from the cdh gene, Taken together, these results demonstrated that CBQ originates from the cdh gene. Furthermore, it is not produced by differential splicing but by a posttranslational, predominantly intracellular, proteolytic cleavage,
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- Thevenin, P. O., et al.
(författare)
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Characterization and activity of supported palladium combustion catalysts
- 2002
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 207:1, s. 139-149
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic activity of Pd supported on gamma-Al2O3, Ba-Al2O3, and La-Al2O3 has been examined in complete oxidation of methane when operating in excess of oxygen. Two different sizes of I'd particles have been considered. Foreign ions have a strong influence with respect to the stabilization of alumina when submitted to a temperature as high as 1000 degrees C. In contrast, no specific effect can be detected when the samples are calcined at 500 degreesC. Interaction with the supported palladium particles, observed during the combustion reaction, has been investigated by X-ray photoelectron Spectroscopy and temperature-programmed oxidation. The difference in combustion activity is attributed to the difference in surface oxidation states of the Pd particles. The presence of foreign ions in the alumina structure results in surface PdO only. When supported on gamma-Al2O3, small amounts of metallic Pd can be detected, resulting in a lower ignition temperature.
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- Zabarovsky, Eugene R, et al.
(författare)
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Restriction site tagged (RST) microarrays : a novel technique to study the species composition of complex microbial systems
- 2003
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Ingår i: Nucleic Acids Research. - Oxford, United Kingdom : Oxford University Press. - 0305-1048 .- 1362-4962. ; 31:16, s. e95-
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a new type of microarray, restriction site tagged (RST), for example NotI, microarrays. In this approach only sequences surrounding specific restriction sites (i.e. NotI linking clones) were used for generating microarrays. DNA was labeled using a new procedure, NotI representation, where only sequences surrounding NotI sites were labeled. Due to these modifications, the sensitivity of RST microarrays increases several hundred-fold compared to that of ordinary genomic microarrays. In a pilot experiment we have produced NotI microarrays from Gram-positive and Gram-negative bacteria and have shown that even closely related Escherichia coli strains can be easily discriminated using this technique. For example, two E.coli strains, K12 and R2, differ by less than 0.1% in their 16S rRNA sequences and thus the 16S rRNA sequence would not easily discriminate between these strains. However, these strains showed distinctly different hybridization patterns with NotI microarrays. The same technique can be adapted to other restriction enzymes as well. This type of microarray opens the possibility not only for studies of the normal flora of the gut but also for any problem where quantitative and qualitative analysis of microbial (or large viral) genomes is needed.
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