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Träfflista för sökning "WFRF:(Johansson Roger) srt2:(1995-1999)"

Sökning: WFRF:(Johansson Roger) > (1995-1999)

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  • Johansson, Agneta (författare)
  • Human mononuclear phagocytes : Production of reactive oxygen species generated by the NADPH oxidase
  • 1995
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Human professional phagocytes constitute the first line of defence against invading microorganisms. With a membrane-bound enzyme system, the NADPH oxidase, these cells generate bactericidal metabolites. Activation of NADPH oxidase results in a generation of reactive oxygen species, e.g. superoxide anion and hydrogen peroxide. These oxygen species constitute an important part of the host defence against invading microbes. The subcellular localization of the NADPH oxidase is of great importance, since activation of plasma-membrane-localized oxidase system results in cellular release of potentially hannful oxygen species in the vicinity of the phagocyte. A regulated intracellular store of NADPH oxidase could focus the bactericidal arsenal on the phagocytosed prey and thereby reduce the risk of extracellular release and tissue damage in the host A new technique was developed that allowed measurement of the release, as well as the intracellular generation, of reactive oxygen species. The technique was used to compare the response induced in different types of phagocytic leukocytes, polymorphonuclear neutrophils, monocytes and macrophages. Stimulating neutrophils with the chemoattraclant peptide fMet-Leu-Phe induce an association of the ligand-receptor complex to the cell cytoskeleton. An event that has been suggested to terminate the activation of NADPH oxidase. Termination of the NADPH oxidase actiVity in monocytes occurs without any association of the complex to the cytoskeleton. Obviously, different mechanisms to terminate the fMet-Leu-Phe-induced oxidase response opemte in monocytes and neutrophils. No qualitative difference was observed between neutrophils and monocytes, with respect to the localization of the respiratory burst. However, macrophages lack the intracellular phase of the respiratory burst, and the molecular background of this difference could be identified by using indirect immunofluorescence and subcellular fractionation to localize the membrane component of the oxidase (cytochrome bsss). In neutrophils, most of the cytochrome b558 as well as most of the donnant oxidase activity, was recovered in the specific granules, whereas only a minor part was recovered in the plasma membrane and secretory vesicles. Considering disintegrated macrophages, NADPH oxidase activity was found exclusively in a fraction enriched in plasma membranes. These results  indicate that macrophages are incapable of intracellular generation of reactive oxygen species due to the absence of a granule-localized pool of the NADPH oxidase. Despite large similarities between different professional phagocytes, fundamental differences are apparent when comparing structural and regulatory processes related to the NADPH oxidase.
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  • Johansson, Jonas, et al. (författare)
  • Time-Resolved Studies of Light Propagation in Crassula and Phaseolus Leaves
  • 1999
  • Ingår i: Photochemistry and Photobiology. - : American Society for Photobiology. - 0031-8655. ; 69:2, s. 242-247
  • Tidskriftsartikel (refereegranskat)abstract
    • Time-resolved transmittance was used to extract in vivo optical properties of leaves of green plants experimentally. In time-resolved transmittance measurements an ultrashort light pulse is directed onto the surface of the object and the transmitted light is measured with a time resolution in the range of picoseconds. A table-top terawatt laser was used to generate 200 fs light pulses at 790 nm with a repetition rate of 10 Hz. The light pulses were focused through a cuvette filled with water to produce white light pulses and optical filters were placed in the beam path to select the wavelength of the light focused onto the leaf surface. The time profiles of the light transmitted through the leaves was recorded with a streak camera having a time resolution of about 2.5 ps. Results from Crassula falcata and Phaseolus vulgaris studied at 550, 670 and 740 nm are reported. The three selected wavelength regions represent medium, high and a low absorption of light, respectively. A library of curves was generated using Monte Carlo simulation, and the absorption and scattering coefficients were extracted by comparison of experimental curves with this library. Our results suggest that in the case of the thin (200 μm) Phaseolus leaves and certainly in the case of the thick (4 mm) Crassula leaves, light scattering plays an important role in light transport through the leaf and should also affect light flux in these leaves.
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  • Johansson, Mikael, et al. (författare)
  • Tumor blood flow and the cytotoxic effects of estramustine and its constituents in a rat glioma model
  • 1997
  • Ingår i: Neurosurgery. - : Oxford University Press. - 0148-396X .- 1524-4040. ; 41:1, s. 237-244
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Estramustine (EaM) is a conjugate of nor-nitrogen mustard (NNM) and 17 beta-estradiol (E2) that has cytotoxic and radiosensitizing effects on experimental malignant glioma. Its mechanism of action is only partly understood. To further investigate the mechanism in vivo, the effects on tumor blood flow (TBF) and tumor growth were analyzed.METHODS: TBF was measured by radioactive microspheres, and tumor growth was measured by weight. Apoptosis was evaluated by in situ end labeling and gel electrophoresis. The effects of the constituents NNM and E2 were also evaluated.RESULTS: EaM increased TBF to 153.8 ml/100 g/min after 3 days and to 153.9 ml/100 g/min after 10 days of treatment, compared with 94.0 ml/100 g/min in untreated controls. Cerebral blood flow did not change after EaM treatment. NNM increased TBF but also showed a tendency to increase cerebral blood flow. E2 increased TBF, whereas cerebral blood flow was unchanged. EaM resulted in a rapid reduction in tumor weight from 230 mg in untreated animals to 146 mg after 3 days of treatment. EaM induced an early transient fragmentation of deoxyribonucleic acid in glioma but not in the normal brain. Neither NNM nor E2 affected tumor weight.CONCLUSION: EaM increases TBF in the BT4C rat glioma model with a concomitant rapid antitumoral effect. The increase in TBF could partially be induced by an estrogen-like action of EaM, but the rapid cytotoxic effect of the drug is obviously attributed to the intact EaM compound. This cytotoxic effect might be attributable to the induction of programmed cell death.
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  • Törngren, Martin, 1963-, et al. (författare)
  • A mechatronics test-bed for embedded distributed real-time control systems
  • 1997
  • Ingår i: Proceedings of IFAC workshop on Algorithms and Architectures in real-time control systems.
  • Konferensbidrag (refereegranskat)abstract
    • A testbed has been developed to be used for research in distributed real-time control systems.The testbed is modular both in mechanics and in control system, allowing a number of robot configurations,control system structures and execution strategies to be implemented and evaluated. The nodes of thecontrol system are currently based on a microprocessor, CAN communication, interfaces to analog anddigital I/O, and motor drive units. The modularity of the nodes allows changes of I/O and communicationsystem, as well as the implementation of different resource structures. To give an idea of the experimentalcapabilities of the testbed, initial experiments in the area of time-varying control systems are described.The research goals include design and experimental evaluation of execution strategies, time-varying controlsystems and development tools for real-time implementation support.
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  • Resultat 1-10 av 11
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