A Berglund

National Veterinary Institute, Sweden, Uppsala, Uppsala, Sweden

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Publications (9)25.96 Total impact

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    ABSTRACT: An increasing number of people in Sweden are claiming that they are hypersensitive to electricity. These patients suffer from skin as well as neurological symptoms when they are near computer monitors, fluorescent tubes, or other electrical appliances. Provocation studies with electromagnetic fields emitted from these appliances have, with only one exception, all been negative, indicating that there are other factors in the office environment that can effect the autonomic and/or central nervous system, resulting in the symptoms reported. Flickering light is one such factor and was therefore chosen as the exposure parameter in this study. Ten patients complaining of electrical hypersensitivity and the same number of healthy voluntary control subjects were exposed to amplitude-modulated light. The sensitivity of the brain to this type of visual stimulation was tested by means of objective electrophysiological methods such as electroretinography and visual evoked potential. A higher amplitude of brain cortical responses at all frequencies of stimulation was found when comparing patients with the control subjects, whereas no differences in retinal responses were revealed.
    Journal of Occupational and Environmental Medicine 02/1997; 39(1):15-22. · 1.80 Impact Factor
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    ABSTRACT: Oscillations of free intracellular calcium [Ca2+]i were seen in individual Jurkat cells as response to a 50 Hz, 0.15 mT magnetic field (MF). In contrast, a CD45-deficient Jurkat cell line was unable to respond to MF stimulation. The phosphatase activity of CD45 has been implicated to regulate p56lck tyrosine kinase activity by removing an inhibitory phosphate. By using Jurkat cells that expressed a chimeric molecule, comprising the cytoplasmic phosphatase domain of CD45, the MF induced calcium response was restored. This showed the necessity for an intact signal transduction pathway leading to a calcium increase as a result of stimulation of cells by MF. Thus, our data suggest that the target for the applied MF are molecules involved in early events in the signalling pathway from the T cell antigen receptor.
    FEBS Letters 09/1995; 370(1-2):118-22. · 3.34 Impact Factor
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    ABSTRACT: We have earlier reported that when a weak 50 Hz MF (magnetic field) was applied, the leukemic T-cell line Jurkat responded with intracellular calcium oscillations [Lindström, et al., J. Cell Physiol., 156 (1993) 395-398]. The result suggested that the MF interfered with the signal transduction, although neither target molecules nor molecular mechanisms are at present known. In this study we found that application of a MF to Jurkat cells resulted in significant increase of inositol 1,4,5-trisphosphate (IP3) levels. Chelation of intracellular calcium ions by BAPTA/AM, did not block the increase of IP3 induced by MF. This result implied that MF-induced Ca2+ oscillations were not due to direct stimulation of the Ca(2+)-dependent phospholipase C-gamma 1 (PLC-gamma 1).
    FEBS Letters 03/1995; 359(2-3):151-4. · 3.34 Impact Factor
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    ABSTRACT: Low-frequency magnetic fields (MF) can increase the cytosolic calcium concentration ([Ca2+]i) in lymphocytes in the same manner as a physiological stimulus such as antibodies directed towards the CD3 complex. In this study, MF with various frequencies and flux densities were used, while [Ca2+]i changes were recorded using microfluorometry with fura-2 as a probe. The applied sinusoidal MF induced oscillatory changes of [Ca2+]i in the leukemic cell line Jurkat in a manner similar to that seen with stimulation by antibodies. The response at 0.15 mT was over a frequency range from 5 to 100 Hz, with a fairly broad peak having its maximum at 50 Hz. The result of testing increasing flux densities at 50 Hz was a threshold response with no effect below 0.04 mT and a plateau at 0.15 mT. On the basis of the characteristic calcium pattern resulting from an applied MF, we suggest that MF influence molecular events in regular signal transduction pathways of T cells.
    Bioelectromagnetics 02/1995; 16(1):41-7. · 1.86 Impact Factor
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    ABSTRACT: Applied weak magnetic fields have been shown to affect cellular activity on several levels, but the mechanisms involved remain elusive. We have decided to study an early signal transduction event in the human T cell line Jurkat; oscillations of free [Ca2+]i, of the type seen by crosslinking the CD3 complex. Cells were exposed to a 50 Hz, 0.1 mT, sinusoidal magnetic field while intracellular free calcium was measured in individual cells, using fura-2 as a probe. An acute response was observed with oscillatory increases in [Ca2+]i, which subsided when the field was turned off. The effect of the magnetic field on [Ca2+]i was comparable to that achieved by an anti-CD3 monoclonal antibody.
    Journal of Cellular Physiology 09/1993; 156(2):395-8. · 3.87 Impact Factor
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    ABSTRACT: The calcium receptor calmodulin interacts with components of the human red cell membrane skeleton as well as with the membrane. Under physiological salt conditions, calmodulin has a calcium-dependent affinity for spectrin, one of the major components of the membrane skeleton. It is apparent from our results that calmodulin inhibits the ability of erythrocyte spectrin (when preincubated with filamentous actin) to create nucleation centers and thereby to seed actin polymerization. The gelation of filamentous actin induced by spectrin tetramers is also inhibited by calmodulin. The inhibition is calcium dependent and decreases with increasing pH, similar to the binding of calmodulin to spectrin. Direct binding studies using aqueous two-phase partition indicate that calmodulin interferes with the binding of actin to spectrin. Even in the presence of protein 4.1, which is believed to stabilize the ternary complex, calmodulin has an inhibitory effect. Since calmodulin also inhibits the corresponding activities of brain spectrin (fodrin), it appears likely that calmodulin may modulate the organization of cytoskeletons containing actin and spectrin or spectrin analogues.
    Biochemistry 03/1988; 27(4):1104-10. · 3.19 Impact Factor
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    A Berglund, L Backman, V P Shanbhag
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    ABSTRACT: The binding of the isolated alpha-subunit of human erythrocyte spectrin to calmodulin is demonstrated by partitioning in aqueous two-phase systems. The affinity of the alpha-subunit for calmodulin is slightly higher than that of the spectrin dimer, whereas the beta-subunit interacts only very weakly. The binding is in all cases calcium-dependent and is abolished on addition of chlorpromazine. At an ionic strength close to physiological conditions, about 1 microM free calcium is required to induce maximum binding of calmodulin to spectrin dimer.
    FEBS Letters 07/1986; 201(2):306-10. · 3.34 Impact Factor
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    ABSTRACT: Calmodulin is shown to interact with human spectrin dimer. The binding was highly calcium-dependent and observed in two different kinds of experiments. Firstly, affinity chromatography of calmodulin on a Sepharose 4B column with immobilized spectrin, and secondly, partition in aqueous two-phase polymer systems. In the column experiments stoichiometric amounts of calmodulin were retained on the spectrin-Sepharose column when micromolar concentrations of calcium were present. The calmodulin bound could be eluted with EGTA. The partition coefficient of calmodulin in an aqueous two-phase polymer system containing calcium was changed upon addition of spectrin, indicating an association between the two proteins. In the absence of calcium, spectrin did not cause any change in the partition behaviour of calmodulin, thus showing that the association requires calcium.
    FEBS Letters 07/1984; 172(1):109-13. · 3.34 Impact Factor
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    ABSTRACT: Interferon-alpha (IFN-alpha) subtypes bind to the same receptor and are expected to have the same biological functions. Whether or not leukocyte IFN, containing six major IFN-alpha proteins had the same anti-tumor effect as one subtype, recombinant IFN-alpha2b, was investigated. Three melanoma lines were treated with both types of IFN, and the effect on proliferation and survival was estimated both after short-term and prolonged treatment. All the melanoma cell lines were sensitive to the antiproliferative effects of both IFN species during short-term treatment. However, upon prolonged culture, the frequency of resistant colony formation was significantly higher in cultures treated with IFN-alpha2b compared to those treated with leukocyte IFN. There was a qualitative difference between the resistant colonies selected by the two IFN species with respect to morphology, growth rate and sensitivity to apoptosis. The development of resistant clones occurred at a lower rate during long-term treatment with leukocyte IFN containing six major subtypes of IFN-alpha as compared to IFN-alpha2b.
    Anticancer research 27(4B):2109-14. · 1.87 Impact Factor

Publication Stats

294 Citations
25.96 Total Impact Points

Institutions

  • 1995
    • National Veterinary Institute, Sweden
      Uppsala, Uppsala, Sweden
  • 1984–1986
    • Umeå University
      • Department of Medical Biochemistry and Biophysics
      Umeå, Västerbotten, Sweden