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S Olsson

Publications and source records attributed to S Olsson.

At least 19 recordsLinked to original sources
PubMed2005

Using phospholipid fatty acid technique to study short-term effects of the biological control agent Pseudomonas fluorescens DR54 on the microbial microbiota in barley rhizosphere.

The biological control agent (BCA) Pseudomonas fluorescens DR54 was applied to seeds (experiment 1) or roots (experiment 2) of barley growing in microcosms, while noninoculated plants served as controls. The fate of the BCA and its effects on the rhizosphere microbial community was evaluated in microcosms destructively sampled at days 2, 4, 6, and 9 after inoculation. In both experiments the number of P. fluorescens DR54 cells decreased immediately after application as enumerated by immunostaining and microscope direct counting. Substrate-induced respiration (SIR) was taken as a measurement of the active microbial biomass, while indicators of the total microbiota (and main taxonomic groups) were obtained using the phospholipid fatty acid (PLFA) technique. In experiment 1, these parameters were unaffected by the relatively small number of BCA cells applied, whereas in experiment 2, the larger BCA input resulted in an enhanced level of both SIR and PLFAs from Gram-negative bacteria (which included the BCA itself). However, at day 9 after inoculation, treatments with P. fluorescens DR54 and controls were similar in all measured parameters in both experiments. This was also illustrated very clearly by principal component analysis of the PLFA data, which in both experiments were able to discriminate between treatments in the first days after BCA inoculation, thus confirming the sensitivity of this method. Laccase activity has a potential as an indicator of fungal stress, e.g., when challenged with an antifungal BCA. This seemed to be supported in experiment 2, where the activity of this enzyme was enhanced four-fold in the BCA treatment at day 2. Our study shows that under the present conditions, P. fluorescens DR54 disappears from the soil and causes only transient effects on the soil microbiota. It also shows that the PLFA technique is a sensitive and reliable monitoring tool in in situ assessment of BCA nontarget effect on indigenous microorganisms in soil.

Fatty Acids↗
PubMed2004

Activation of caspase-like activity and poly (ADP-ribose) polymerase degradation during sporulation in Aspergillus nidulans.

Mycelium vacuolization, protein degradation, and as the final stage autolysis, often accompanies developmental changes in fungi and similarities between autolysis and apoptosis have previously been suggested. Caspases are the key executors of apoptosis and in this study caspase-like activities were detected in protein extracts from Aspergillus nidulans during sporulation. This was shown by hydrolysis of the fluorescent DEVD- and IETD-AFC peptide substrates specific for caspase 3- and 8-like activities, respectively. These activities were repressed by the caspase 3 and 8 specific irreversible peptide inhibitors DEVD-fmk and IETD-fmk, but were not affected by the unspecific inhibitor E-64. Isoelectric focusing of protein extracts followed by activity staining revealed the presence of two bands with caspase-like activity. One of the proteins degraded both caspase 3 and caspase 8 specific substrates whereas the other only degraded the caspase 8 substrate. Searches in an A. nidulans genome database revealed two genes encoding metacaspase proteins with predicted sizes of 45 kDa that could be responsible for the measured caspase-like activities. The searches also found a single gene encoding a poly (ADP-ribose) polymerase (PARP) protein with a predicted size of 81 kDa. PARP is one of the known target proteins inactivated by caspase degradation in animal cells. Western blotting of fungal extracts using a bovine PARP antibody confirmed the presence of a fungal PARP-like protein of about 81 kDa. By Western blotting it was shown that this PARP-like protein band was present only at early time points until the start of conidia formation and the accompanying increase in caspase-like activity. Thereafter, a degradation product of about 60 kDa appeared indicating that the degradation of the fungal PARP-like protein was specific. The PARP antibody also recognized an 85 kDa protein band that was not degraded, and which conceivably represents a modified form of the 81 kDa PARP. Fungal extracts high in caspase-like activity could degrade both the fungal 81 kDa PARP and bovine PARP. In the presence of the caspase 3 inhibitor DEVD-fmk this degradation was delayed. Thus, as in animal apoptotic cells, caspase activities are involved in fungal mycelium self-activated proteolysis.

Animals↗
PubMed2004

Ammonium formate, a compound for sensitive EPR dosimetry.

Alanine EPR dosimetry has been applied successfully when measuring intermediate and high radiation doses. Although the performance of alanine dosimetry is being improved, the sensitivity of the material is too low for a fast and simple low- dose determination. Here we present the results using ammonium formate as an EPR dosimeter material. Ammonium formate is seven times more sensitive than alanine, using spectrometer settings optimized for the latter. Deuterated ammonium formate is found to be more than eight times more sensitive than alanine. Analysis of signal stability with time shows that the ammonium formate signal is stable by 5 min after irradiation and that no change in signal intensity is found during 8 days. The atomic composition of ammonium formate is closer to that of tissue than alanine, and thus the energy dependence is smaller than that of alanine at photon energies below 200 keV. Power saturation studies indicate that the energy transfer between the spins and the lattice is fast in ammonium formate, which gives the possibility of using high microwave power without saturation to further increase the sensitivity. These results suggest that ammonium formate has some important properties required of an EPR dosimeter for applications in dosimetry in the dose range typical for radiation therapy.

Alanine↗
PubMed2003

Accumulation of radionuclides from radioactive substrata by some micromycetes.

Overgrowing (interaction) and dissolution of intact and milled hot particles by various micromycetes were studied under laboratory conditions. Hot particles used for the investigation originated from the Chernobyl accident release and atomic bomb testing sites. The micromycetes investigated were mitosporic fungi mainly isolated from the Chernobyl site and vicinity. Most of the fungal species and strains showed a tendency to grow towards the hot particle, overgrow it and dissolve it after prolonged contact. The accumulation (absorption and adsorption) of radionuclides from intact hot particles was generally more intensive for (152)Eu than for (137)Cs by a factor of about 2.6-134, while in experiments with milled samples the (152)Eu and (137)Cs accumulation was similar, except for some fungal species, which showed higher (152)Eu than (137)Cs sorption. It could be shown that the main factors influencing Cs and Eu accumulation in fungi are: fungal species and strains and the size and composition of the hot particle.

Cesium Radioisotopes↗
PubMed2003

Low concentrations of cytokines produced by allergen-stimulated peripheral blood mononuclear cells have potent effects on nasal polyp-derived fibroblasts.

Accumulating data show that fibroblasts are important regulators in the development and maintenance of allergic airway inflammation. However, most studies so far have used individual recombinant cytokines in high concentrations, unlikely to be found in vivo. We aimed to investigate how cytokines produced by peripheral blood mononuclear cells (PBMC) affect fibroblast functions. Primary airway fibroblasts where incubated with allergen-stimulated or non-stimulated PBMC supernatants from allergic patients. The levels of cytokines in PBMC supernatants were measured and the expression of CD54, CD40 and CD106 as well as the production of eotaxin, interleukin (IL)-6 and IL-8 were assessed in fibroblasts. Although the levels of single cytokines measured in PBMC supernatants were low, a significant up-regulation of the surface molecules as well as of IL-6 and IL-8 production was found in fibroblasts cultured with allergen-stimulated PBMC supernatants as compared to non-stimulated, while the increase in eotaxin production was not significant. The evaluation of correlations between cytokines produced by PBMC and effects seen on fibroblasts did not indicate a crucial role for any single cytokine. Furthermore, the addition of comparably low concentrations of recombinant interferon (rIFN)-gamma or recombinant tumour necrosis factor (rTNF)-alpha did not induce the same effects as PBMC supernatants, the only exception being TNF-alpha as a direct inducer of CD54 expression. Our results show that synergistic mechanisms has a more important role than single mediators, highlighting important differences between in vitro experiments, where effects of individual mediators are studied, versus the actual situation in vivo.

Cells, Cultured↗
PubMed2002

Radiation dose measurements with alanine/agarose gel and thin alanine films around a 192Ir brachytherapy source, using ESR spectroscopy.

Alanine/agarose gel and alanine films in stacks have been used for measurements of absorbed dose around an HDR 192Ir source in a vaginal cylinder-applicator, with and without a 180 degrees tungsten shield. The gel and the films were analysed by means of ESR spectroscopy and calibrated against an ion chamber in a 4 MV photon beam to obtain absolute dose values. The gel serves as both dosimeter and phantom material, and the thin (130 microm) films are used to achieve an improved spatial resolution in the dose estimations. Experimental values were compared with Monte Carlo simulations using two different codes. Results from the measurements generally agree with the simulations to within 5%, for both the alanine/agarose gel and the alanine films.

Alanine↗
PubMed2002

New materials for ESR dosimetry.

New materials for electron spin resonance (ESR) dosimetry have been investigated with the aim to find systems more sensitive than L-alanine accepted as a standard for high dose determinations. Among the investigated systems ammonium tartrate, 2-methylalanine, salts of formic acids and dithionates have been found to be more sensitive than alanine by a factor 2-10. The lower limit applies to tissue equivalent materials, while much higher sensitivities were obtained with formates and dithionates containing heavier atoms. The increased sensitivity was mainly attributed to suitable ESR properties of the room temperature stable radicals as regards spectral shape (narrow lines, little or no hyperfine structure) and microwave saturation properties (short relaxation times). The radical structures have when necessary been clarified by ENDOR spectroscopy, while the saturation properties have been screened by pulsed ESR measurements.

Alanine↗
PubMed2001

Diffusion, utilisation and regional variations in the use of CT and MRI in Sweden.

To study the diffusion, access, use, and utilisation of Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI) in Sweden a national survey was carried out by a written questionnaire mailed to all public and private hospitals and clinics in 1997. To get a survey of CT and MRI in other countries a request asking for number of units was sent to recognised authorities and individuals in selected countries. CT and MRI were introduced in Sweden in 1973 and 1984 respectively. The diffusion of CT and MRI in Sweden are amongst the highest in the world. Considering the small size of the country and the medical community (e.g. facilitating transparency in indications for use of CT and MRI) and the relatively homogeneous health care system (tax based finance system) the regional variations in access, use, and utilisation of CT and MRI were surprisingly large. For example: In 1996 the number of CT examinations per 100.000 inhabitants varied from 3.344 to 4.705 between the regions. The MRI examinations varied from 751 to 1.858. Some of the differences may be explained by demographic factors. Also, reimbursement policies by the county councils for CT and MRI examinations varied which gave different incentives for patient referrals. However, to explain most of the differences more research is needed. Factors like proportion of elderly amongst the populations in the regions and other socio-demographic factors, proportion of research orientation of examinations and national medical specialities, organisation of the health care, etc. may to a greater extent explain the differences.

Health Services Accessibility↗
PubMed2001

Three-dimensional outgrowth of a wood-rotting fungus added to a contaminated soil from a former gasworks site.

The capability of wood-rotting fungi (WRF) to colonise contaminated soil is an important fungal characteristic in the development of WRF-based soil bioremediation, it is also important to have methods that monitor the presence of the WRF in the soil. In this lab-scale study, it was shown that it was possible to re-capture, localise and identify a brown-rot fungus, Antrodia vaillantii, after it has been inoculated into, and grown in, a contaminated soil from a former gasworks site. The three-dimensional outgrowth of A. vaillantii was monitored by allowing it to grow into fungicide-treated wood baits, temporarily placed in the soil. After two weeks, the baits were withdrawn from the soil and surface sterilised with hydrogen peroxide to favour fungi growing inside baits, i.e., A. vaillantii. After subsequent plating of baits on selective agar medium the presence of A. vaillantii was confirmed with PCR/RFLP. A. vaillantii was found to be viable throughout the 54 days long study and exhibited a surface growth pattern similar to other well-known cord-forming basidiomycetes. Firstly, the upper part of the soil closest to the place of inoculation was colonised, however, over a period of time, the area of colonisation spread deeper into the soil. The detection method employed in the current study gave a conservative estimate of the fungal proliferation and did not require extensive sampling. Its use could be applicable in both applied research, such as soil bioremediation, and in pure microbial ecology studies.

Benomyl↗
PubMed2001

T cell responses to recombinant isoforms, synthetic peptides and a mutant variant of Lep d 2, a major allergen from the dust mite Lepidoglyphus destructor.

BACKGROUND: The dust mite Lepidoglyphus destructor is an important cause of allergic reactions to dust, especially in farming environments. Two isoforms, recombinant (r)Lep d 2.01 and rLep d 2.02, of the major allergen Lep d 2, have previously been expressed as recombinant proteins. These isoforms differ 10.4% at the amino acid level. Furthermore, a mutant form of Lep d 2.01 (rLep d 2.6Cys) with a highly reduced IgE reactivity, has also been produced. OBJECTIVE: To investigate the T cell responses to the recombinant isoforms of Lep d 2, the Lep d 2.6Cys mutant and peptides of Lep d 2, in allergic and non-allergic individuals. METHODS: Peripheral blood mononuclear cells from 18 allergic and 16 non-allergic individuals were stimulated with the different antigens and the proliferative responses were measured. The cytokine production (interleukin (IL)-4, IL-5 and interferon (IFN)-gamma) were measured by ELISA. RESULTS: Higher T cell proliferation was measured to isoform 01 than to 02 in 28/34 subjects. The responses to rLep d 2.6Cys were lower than to isoform 01 in most subjects, but higher than to Lep d 2.02. Two immuno-dominant peptides, corresponding to amino acid residue 11-25 and 61-75 were identified. The atopic subjects produced significantly lower IFN-gamma in response to Lep d 2.01 as compared to the non-atopics. CONCLUSIONS: There was a significant difference in T cell response between the two isoforms of rLep d 2. The hypoallergenic mutant rLep d 2.6Cys was able to evoke a T cell response with a magnitude which is between the two isoforms. Amino acid residue 11-25 and 61-75 are the most frequently recognized parts of Lep d 2 and are likely to contain the immuno-dominant T cell epitopes.

Adult↗
PubMed2001

Induction of laccase activity in Rhizoctonia solani by antagonistic Pseudomonas fluorescens strains and a range of chemical treatments.

Fungi often produce the phenoloxidase enzyme laccase during interactions with other organisms, an observation relevant to the development of biocontrols. By incorporating the laccase substrate 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) into agar, we analyzed laccase induction in the plant-pathogenic fungus Rhizoctonia solani when paired against isolates of the soil bacterium Pseudomonas fluorescens. Substantial induction of R. solani laccase was seen only in pairings with strains of P. fluorescens known to produce antifungal metabolites. To study laccase induction further, a range of chemical treatments was applied to R. solani liquid cultures. p-Anisidine, copper(II), manganese(II), calcium ionophore A23187, lithium chloride, calcium chloride, cyclic AMP (cAMP), caffeine, amphotericin B, paraquat, ethanol, and isopropanol were all found to induce laccase; however, the P. fluorescens metabolite viscosinamide did not do so at the concentrations tested. The stress caused by these treatments was assessed by measuring changes in lipid peroxidation levels and dry weight. The results indicated that the laccase induction seen in pairing plate experiments was most likely due to calcium or heat shock signaling in response to the effects of bacterial metabolites, but that heavy metal and cAMP-driven laccase induction was involved in sclerotization.

Antibiosis↗
PubMed2001

A hypoallergenic derivative of the major allergen of the dust mite Lepidoglyphus destructor, Lep d 2.6Cys, induces less IgE reactivity and cellular response in the skin than recombinant Lep d 2.

BACKGROUND: The major allergen of the dust mite Lepidoglyphus destructor, Lep d 2, has been produced as a recombinant allergen (rLep d 2) with IgE reactivity both in vivo and in vitro. A modified form of rLep d 2 (rLep d 2.6Cys) obtained by site-directed mutagenesis has been shown to have a reduced IgE reactivity in vitro. In this study we have compared the ability of rLep d 2 and rLep d 2.6Cys to elicit positive skin prick tests and cellular responses among L. destructor-sensitized subjects. METHODS: Seventeen subjects were skin prick-tested with rLep d 2, rLep d 2.6Cys, histamine and negative controls and 17-20 h later skin biopsy specimens were taken from the skin prick-tested sites. The biopsy specimens were stained immunohistochemically for EG2+, CD3+, CD1a+, mast cell tryptase+, and IgE+ cells. Dermal cell infiltrates were judged in hematoxylin and eosin staining. Total IgE and allergen-specific IgE were determined by CAP-RAST. RESULTS: Compared to rLep d 2, rLep d 2.6Cys induced significantly smaller and fewer skin prick test reactions (p < 0.001) and dermal cell infiltrates (p < 0.05). Further, rLep d 2.6Cys induced fewer EG2+ cells (p < 0.001) but more tryptase+ cells (p < 0.05) than rLep d 2. A positive RAST to rLep d 2 was obtained for 88.2% of the subjects, while only 35.2% displayed a positive RAST to rLep d 2.6Cys. CONCLUSION: This study demonstrates that rLep d 2.6Cys is less able to evoke IgE-mediated reactions and cellular responses, as measured both in skin and in serum, than rLep d 2. In the future this hypoallergenic derivative may be a promising candidate molecule for immunotherapy of L. destructor-allergic patients.

Adult↗
PubMed2001

IgG1, IgG4 and IgE antibody reactivity to mutant forms of the major dust mite allergen Lep d 2 among atopic and nonatopic subjects naturally exposed to Lepidoglyphus destructor.

BACKGROUND: Lepidoglyphus destructor is a common dust mite causing IgE-mediated sensitization. The major allergen, Lep d 2, has previously been cloned and expressed as several double Cys to Ser mutants with the purpose of producing hypoallergenic variants for immunotherapy. Our aim was to investigate the reactivity pattern of IgG1, IgG4 and IgE antibodies to wild-type (wt) rLep d 2 and four mutants among atopic and nonatopic subjects in relation to sensitization and exposure to L. destructor. METHODS: Inhibition and sandwich ELISA were used to compare IgG1, IgG4 and IgE antibody reactivities to rLep d 2 variants in serum of 20 atopic and 18 nonatopic farmers naturally exposed to L. destructor. A group of 22 urban subjects served as controls. RESULTS: Atopic farmers demonstrated correlating IgE and IgG4 levels to rLep d 2(wt) (rs = 0.70; p < 0.0001) which were significantly (p < 0.0001) higher than those of nonatopic farmers and urban controls. No IgG4 antibodies were detected in nonatopic farmers despite chronic allergen exposure. A parallel reactivity pattern of IgE and IgG4 to all rLep d 2 mutants was observed. The mutant lacking all 3 disulfide bonds, rLep d 2.6Cys, demonstrated neither any IgE nor IgG4 reactivity. In contrast, IgG1 antibodies had a different reactivity pattern and were detected among most subjects irrespective of atopy, exposure to L. destructor or disulfide impairments in rLep d 2. Moreover, IgG1 levels to rLep d 2(wt) and rLep d 2.6Cys correlated (n = 60; rs = 0.65; p < 0.0001). CONCLUSIONS: IgE/IgG4 Ab to rLep d 2 were restricted to atopic farmers and demonstrated parallel recognition patterns of conformational epitopes. In contrast, IgG1 antibodies are ubiquitously found and mainly recognize sequential structures. The observed isotypic difference and interindividual variation in antibody specificities among atopic and nonatopic subjects imply careful investigation of hypoallergenic variants destined for immunotherapy.

Allergens↗
PubMed2000

Viscosinamide-producing Pseudomonas fluorescens DR54 exerts a biocontrol effect on Pythium ultimum in sugar beet rhizosphere.

Growth inhibition of the root pathogen Pythium ultimum by the biocontrol agent Pseudomonas fluorescens DR54 inoculated on sugar beet seeds was studied in a soil microcosm. Plant emergence was followed, together with bacterial rhizosphere colonization, antibiotic production and effects on fungal growth. P. fluorescens DR54 inoculation of the P. ultimum-challenged seeds improved plant emergence after 7 days compared to a control without the biocontrol strain. At this time, P. fluorescens DR54 was the dominating colony-forming pseudomonad in rhizosphere soil samples from inoculated seedlings as shown by immuno-staining with a strain specific antibody. Viscosinamide, a cyclic lipopeptide, which has previously been identified as a major antagonistic determinant produced by P. fluorescens DR54 and shown to induce physiological changes in P. ultimum in vitro, could be detected in the rhizosphere samples. The impact of P. fluorescens DR54 on the growth and activity of P. ultimum was studied by direct microscopy after staining with the vital fluorescent dyes Calcofluor white and fluorescein diacetate. P. fluorescens DR54 caused reduction in P. ultimum mycelial density, oospore formation and intracellular activity. Further, Pythium oospore formation was absent in the presence of P. fluorescens DR54. A striking effect on zoospore-forming indigenous fungi was also observed in microcosms with P. fluorescens DR54 and, thus, where viscosinamide could be detected; a large number of encysted zoospores were seen in such microcosms both with and without P. ultimum infections. In vitro studies confirmed that purified viscosinamide induced encystment of Pythium zoospores.

Journal Article↗
PubMed2000

Translocation induced outgrowth of fungi in nutrient-free environments.

The study of alternatives to chemical methods of nematode control in agriculture has received significant recent interest. One such method is biological control using nematode trapping fungi such as Arthrobotrys superba. To understand how these fungi can be implemented as effective nematicides, it is essential to study their outgrowth into soil from localized nutrient resources. In this paper, we use a mathematical model to investigate the outgrowth of fungi into an environment essentially without available nutrients capable of supporting net growth. By comparing model solutions with experimental results, we show that in such circumstances, continual mycelial expansion can only be obtained if internal metabolites are actively translocated through the mycelium. Predictions are made concerning the maximal extension possible from a given quantity of nutrients and a testable functional relationship between the two is derived. Using this modelling technique we are able to map not only biomass extent but also biomass distribution at each stage. The type of environmental heterogeneity investigated here is encountered by many species of fungi in nature and is of relevance for the introduction of specific fungi into soil for biological control or bioremediation purposes.

Animals↗
PubMed2000

Growth of Arthrobotrys superba from a birch wood resource base into soil determined by radioactive tracing.

The ability of a nematode-trapping fungus to establish in field soil is an important characteristic when considering its use as a biological control agent. The outgrowth of the nematode-trapping fungus Arthrobotrys superba from wood was recorded by labelling the fungus with [(14)C]3-O-methylglucose and [(32)P]orthophosphoric acid and by using the soil sprinkling method. The fungus reached a distance of 7-8 cm during 25 days in heat-treated (60 degrees C) soil, detected by either radioactive tracing or the soil sprinkling technique. The two labelled compounds were co-distributed at all sampling times (r(2)=0.946) which indicates that the glucose pool (as methylglucose) and phosphorus content were correlated throughout the mycelium. In natural, non-heat-treated soil the fungus reached a distance of 1.5 cm from one disc of birch wood after 30 days, while it reached 3.2 cm during the same period when the food base was a pile of five inoculated discs. The experiments showed, for the first time, that a nematophagous fungus, A. superba, can grow out into soil from a piece of wood and supported by nutrients translocated from the resource base to the edge of the mycelium.

Journal Article↗