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1.
Evolution of antigenic diversity in the tick‐transmitted bacterium Borrelia afzelii: a role for host specialization? 下载免费PDF全文
L. Råberg Å. Hagström M. Andersson S. Bartkova K. Scherman M. Strandh B. Tschirren 《Journal of evolutionary biology》2017,30(5):1034-1041
Antigenic diversity in pathogenic microbes can be a result of at least three different processes: diversifying selection by acquired immunity, host–pathogen coevolution and/or host specialization. Here, we investigate whether host specialization drives diversity at ospC (which encodes an immunodominant surface protein) in the tick‐transmitted bacterium Borrelia afzelii. We determined prevalence and infection intensity of ospC strains in naturally infected wild mammals (rodents and shrews) by 454 amplicon sequencing in combination with qPCR. Neither prevalence nor infection intensity of specific ospC strains varied in a species‐specific manner (i.e. there were no significant ospC × host species interactions). Rankings of ospC prevalences were strongly positively correlated across host species. Rankings of ospC infection intensities were correlated more weakly, but only in one case significantly < 1. ospC prevalences in the studied mammals were similar to those in ticks sampled at the study site, indicating that we did not miss any mammal species that are important hosts for specific ospC strains. Based on this, we conclude that there is at best limited host specialization in B. afzelii and that other processes are likely the main drivers of ospC diversity. 相似文献
2.
This study evaluates causal relationships between chronic exposure of fish to metals and effects at different levels of biological organization based on a weight-of-evidence approach. Criteria for evaluation of causality were strength, consistency, and specificity of the association, as well as biological gradient and plausibility. Field sampling was conducted three times between 1998 and 2000, in Furnas Stream, impacted by an abandoned lead mine, and in three other locations, including two reference and one impacted sites. Levels of Pb, Zn, Cd, and Ag in sediments from the Furnas Stream exceeded background levels, and their concentrations were above sediment quality guidelines. Residual levels of metals in fish tissue were high enough to indicate reduced growth, reproduction and/or survival according to toxicological benchmarks. Lead-induced biochemical changes (ALA-D activity depletion) were observed in two species of siluriform catfish. The condition factor of a predatory catfish was reduced, and the percentage of prey generalists was higher in Furnas than at the noncontaminated sites. Reduction in fish community diversity and density was observed. Integration of data provided supporting evidence that observed effects on fish from the Furnas Stream resulted from long-term exposure to metals, however influences from other stressors cannot be ruled out. 相似文献
3.
S E Andersson C Zackrisson A Hemsén J M Lundberg 《Biochemical and biophysical research communications》1992,188(3):1116-1121
Intratracheal instillation of Sephadex beads induced a long-lasting inflammation in the rat lung as seen by an increase in lung weights. Repeated instillation enhanced this reaction and increased lung endothelin-1 content 3.5 times. Budesonide given s.c. abolished these effects and even reduced basal endothelin-1 content by 72%. The tissue content of the sensory neuropeptide neurokinin A were unaffected by both treatments. Endothelin has been proposed to play a part in the pathogenesis of bronchial asthma. If it is so, the ability of budesonide to reduce endothelin-1 content could thus be added to the list of beneficial effects of glucocorticosteroids in these conditions. 相似文献
4.
The elimination from the blood of 51Cr-labelled mouse erythrocytes modified with trinitrophenyl (TNP) groups was followed in mice. After 24 hours, when a stable concentration of the labelled erythrocytes has been attained, monoclonal anti-TNP-antibodies were given intravenously, either in free, soluble form, or bound to microparticles containing immobilized protein A. The anti-TNP-antibodies induced a rapid elimination of the TNP- and 51Cr-labelled erythrocytes. Over the 8-hours time period studied, the elimination rate was significantly faster when the antibodies were administered bound to the particles. After the elimination of the target cells, the radioactivity was found in the liver, spleen and bone marrow. These results and relevant control experiments indicate that a solid carrier 1. can be directed to a specific target cell with a specific antibody and 2. can induce a rapid elimination of the target cell from the circulation. 相似文献
5.
Karl E. Andersson George S. Drummond Umberto Freddara Mohinder K. Sardana Shigeru Sassa 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(3):289-299
The effects of single large doses of the porphyrin-heme precursor ?d-aminolevulinic acid on tissue porphyrins and on δ-aminolevulinate synthase and heme oxygenase, the rate-living enzymes of liver heme synthesis and degradation respectively, were studied in the chick embryo in ovo, in the mouse and in the rat. δ-Aminolevulinic acid treatment produced a distinctive pattern characterized by extensive tissue porphyrin accumulation and alterations in these rate-limiting enzymes in the liver. Repression of basal or allylisopropylacetamide-induced liver δ-aminolevulinate synthase was observed and, in the mouse and the rat, induction of liver heme oxygenase after δ-aminolevulinic acid treatment, in a manner similar to the known effects of hemin on these enzymes. In the chick embryo liver in ovo heme oxygenase was substantially higher than in rat and mouse liver, and was not significantly induced by δ-aminolevulinic acid or other compounds, including hemin, CS2 and CoCl2. Levulinic acid, an analogue of δ-aminolevulinic acid, did not induce heme oxygenase in mouse liver. δ-Aminolevunilic acid treatment did not impair ferrochelatase activity but was associated with slight and variable decreases in liver cytochrome P-450. Treatment of chick embryos with a small ‘priming’ dose of 1,4-dihydro-3,5-dicarbethoxycollidine, which impairs liver ferrochelatase activity, accentuated porphyrin accumulation after δ-aminolevulinic acid in the liver. These observations indicate that exogenous δ-aminolevulinic acid is metabolized to porphyrins in a number of tissues and, at least in the liver, to a physiologically significant amount of heme, thereby producing an increase in the size of one or more of the heme pools that regulate both heme systhesis and degradation. It is also possible than when δ-aminolevulinic acid is markedly overproduced in vivo it may be transported to many tissues and re-enter the heme pathway and alter porphyrin-heme metabolism in cells and tissues other than those in which its overproduction primarily occurs. 相似文献
6.
Anna Nilsson Thomas E. Fehniger Lena Gustavsson Malin Andersson Kerstin Kenne Gy?rgy Marko-Varga Per E. Andrén 《PloS one》2010,5(7)
Readouts that define the physiological distributions of drugs in tissues are an unmet challenge and at best imprecise, but are needed in order to understand both the pharmacokinetic and pharmacodynamic properties associated with efficacy. Here we demonstrate that it is feasible to follow the in vivo transport of unlabeled drugs within specific organ and tissue compartments on a platform that applies MALDI imaging mass spectrometry to tissue sections characterized with high definition histology. We have tracked and quantified the distribution of an inhaled reference compound, tiotropium, within the lungs of dosed rats, using systematic point by point MS and MS/MS sampling at 200 µm intervals. By comparing drug ion distribution patterns in adjacent tissue sections, we observed that within 15 min following exposure, tiotropium parent MS ions (mass-to-charge; m/z 392.1) and fragmented daughter MS/MS ions (m/z 170.1 and 152.1) were dispersed in a concentration gradient (80 fmol-5 pmol) away from the central airways into the lung parenchyma and pleura. These drug levels agreed well with amounts detected in lung compartments by chemical extraction. Moreover, the simultaneous global definition of molecular ion signatures localized within 2-D tissue space provides accurate assignment of ion identities within histological landmarks, providing context to dynamic biological processes occurring at sites of drug presence. Our results highlight an important emerging technology allowing specific high resolution identification of unlabeled drugs at sites of in vivo uptake and retention. 相似文献
7.
Rats were trained to run spontaneously, without stress, in running wheels. The running activity increased gradually and could reach a plateau of 7 km/night after 3–4 weeks. During the first hour of running in the dark phase the squeak threshold increased significantly and remained high in the morning. The degree of increased threshold was correlated to the amount of running activity. The squeak threshold declined during the following 6 hours of inactivity. A rapid decrease in threshold occurred after naloxone (1–2 mg/kg i.p.). It is suggested that long-lasting muscle exercise (e.g. jogging), acupuncture, and low frequency electrical stimulation of afferent nerve fibres produce discharges in muscle afferents which influence central endorphin mechanics giving analgetic effects. 相似文献
8.
9.
Volkmar Passoth Ann-Christin Andersson Matilda Olstorpe Bart Theelen Teun Boekhout Johan Schnürer 《Antonie van Leeuwenhoek》2009,96(4):635-643
Two yeast strains isolated in 2007 from fermented pig feed were studied, including the analysis of sequences of the D1/D2
and ITS-regions of the rDNA-repeats, their morphology and nutritional physiology. Sequence comparison of the D1/D2 and ITS
regions demonstrated that the strains do not belong to any known species. Therefore, a new species, Cryptococcus cerealis with the type strain CBS 10505, is proposed. The species belongs to Filobasidiales (Agaricomycetes, Basidiomycota), and has
Cryptococcus saitoi as the closest related species. The new species is psychrophilic, showing significant growth at 4 and 10°C. 相似文献
10.