| 1. |
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| 2. |
- Ekelund, Nils, 1956-, et al.
(författare)
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Chromophore rotation in 124-k Dalton Avena sativa phytochrome as measured by light changes in linear dichroism
- 1985
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Ingår i: Photochemistry and Photobiology. - : Wiley. - 0031-8655 .- 1751-1097. ; 41, s. 221-223
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Tidskriftsartikel (refereegranskat)abstract
- From light‐induced changes in linear dichroism, we have calculated the rotation of the long‐wavelength‐absorbing transition moment that occurs during phototransformation of 124‐kilodalton Avena sativa phytochrome. Phytochrome was purified to homogeneity and immobilized onto Sepharose beads covalently coated with antibodies against A. sativa phytochrome. Changes in linear dichroism were induced by plane‐polarized red or far‐red light and measured by the absorbance differences at 660 and 730 nm using a dual‐wavelength spectrophotometer equipped with polarizing filters in the measuring beams. From such measurements, we calculate a rotation angle of 31o (or 149o) during photoconversion of Pr to Pfr and 30o (or 150o) during photoconversion of Pfr to Pr. These values are similar to the value of 32o (or 148o) reported earlier for the rotation of the transition moment of “large”A. sativa phytochrome (? 120 kilodalton) isolated under conditions that did not preclude post homogenization proteolysis of the 124 kilodalton molecule.
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| 3. |
- Ekelund, Nils, 1956-
(författare)
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Effects of calcium channel blockers and DCMU on motility and the photophobic response of Gyrodinium dorsum
- 1989
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Ingår i: Archives of Microbiology. - 0302-8933 .- 1432-072X. ; 151, s. 187-190
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the calcium channel blockers, verapamil, diltiazem and lanthanum ions and the Ca2+ dependency on motility as well as the photophobic response (stop-response) of Gyrodinium dorsum were studied. At Ca2+ concentrations below 10-3 M, motility was inhibited. La3+ inhibits the stop-response, in contrast to verapamil and diltiazem. The only calcium channel blocker that increased the amount of non-motile cells was verapamil. The results indicate that motility are Ca2+ dependent and that the stop-responses of G. dorsum could be affected by extracellular Ca2+. Effects of the photosythesis inhibitor (DCMU) on the stop-response was also determined. With background light of different wavelength (614, 658 and 686 nm) the stop-response increased. DCMU inhibited this effect of background light. Negative results with the monoclonal antibody Pea-25 directed to phytochrome and the results with DCMU, indicate that the stop-response of G. dorsum is coupled to photosynthesis rather than to a phytochrome-like pigment. Oxygen evolution, but not cell movement, was completely inhibited by 10-6 M DCMU.
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| 4. |
- Ekelund, Nils, 1956-
(författare)
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Ljusrörelser hos mikroorganismer
- 1988
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Ingår i: Svensk Botanisk Tidskrift. - 0039-646X. ; 82, s. 333-336
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 5. |
- Ekelund, Nils, 1956-, et al.
(författare)
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Photomovement and photobleaching in two Gyrodinium species
- 1988
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Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 29, s. 1109-1114
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Tidskriftsartikel (refereegranskat)abstract
- The phototactic orientation in Gyrodinium dorsum and G. aureolum has been analyzed. Both species show only positive phototaxis with an optimum at about 300 W-m–2. The mechanism of photoorientation does not seem to be based on a dichroic orientation of the photoreceptor pigments as in the flagellate Euglena gracilis. Photobleaching experiments have shown a far higher resistance toward continuous irradiation at even high fluence rates than in other flagellates which is in good agreement with the exclusive behavior of positive phototaxis.
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| 6. |
- Ekelund, Nils, 1956-, et al.
(författare)
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Photophobic stop-response in a dinoflagellate - modulation by preirridation
- 1987
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 70:3, s. 394-398
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Tidskriftsartikel (refereegranskat)abstract
- Gyrodinium dorsum Kofoid responds photophobically to flashes of blue light. The photophobic response consists of a cessation of movement (stop-response). Without background light and after a flash fluence above 10 J m-2, 75-85% of the cells show a stop-response, only only 50% of the cells show this response at 5 J m-2. With a flash fluence of 5 J m-2, background light of different wavelengths either increases (614 nm, 5.5-18.2 .mu.mol m-2 s-1) or decreases (700 nm, 18.4-36.0 .mu.mol m-2 s-1) the stop-response. Two hypotheses for the mechanism of the modulation by background light of the photophobic response are discussed: an effect of light on the balance of the photosynthetic system (PS I/PS II) or an effect on a phytochrome-like pigment (Pr /Pfr). This study supports the idea that a phytochrome-like pigment works in combination with a blue light-absorbing pigment. It was also found that cells of Gyrodinium dorsum cultured in red light (39.8 .mu.mol m-2) had a higher absorption in the red region of the absorption spectra than those cultured in white light (92.7 .mu.mol m-2).
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| 7. |
- Ekelund, Nils, 1956-, et al.
(författare)
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Phototactic responses of Chlamydomonas reinhardtii in electric fields
- 1988
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 73, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- Chlamydomonas reinhardtii Dangeard strain Göttingen 11 – 32(+) responds both phototactically and galvanotactically. If electric fields and a light stimulus of 496 nm were applied simultaneously, phototaxis persisted but the response was modified. Field lines perpendicular to the phototactic direction of movement inhibited phototaxis. If the field lines were parallel to the light direction, the effect depended on the position of the poles. When the cathode faced the light, an increase of the phototactic reaction values was observed. In this case electric fields enhanced positive phototaxis with increasing voltages from 3 V up to 12 V. If the cathode was on the opposite side, positive phototactic movement was inhibited. The maximum inhibition was found at 12 V. At this voltage positive phototaxis was measured neither at low nor at high fluence rates, and positive phototaxis was shown only between 0.1 and 1.5 W m−1.
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| 8. |
- Ekelund, Nils, 1956-
(författare)
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Öresund
- 1989
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Rapport (populärvet., debatt m.m.)
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| 9. |
- Forslind, B, et al.
(författare)
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Assessment of Qualitative and Quantitative Data From Pathological Hairs : A Critical-evaluation of Scanning Electron-microscope and Proton-induced X-ray-emission Analyses
- 1987
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Ingår i: Scanning Microscopy. - : Scanning Microscopy Int. - 0891-7035. ; 1:1, s. 159-167
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of single hair fibres in genetic disorders is a desirable complement to the clinical diagnosis. The scanning electron microscope (SEM) allows detailed study of the surface morphology of hair fibres which may explain some mechanical characteristics of the pathological hair. Quantitative elemental data may indicate biochemical or metabolic abnormalities. In this preliminary study we assess the feasibility of combining SEM and proton induced X-ray emission (PIXE) analysis on single hair fibres from 12 cases of genetic disease influencing the integument status. We conclude that SEM is a valuable tool in the analysis of hair pathology. The macro-PIXE technique involves some methodological and technical problems which in many cases are likely to be solved by using a proton microbeam. However, this means that routine methods have to be abandoned and careful selection of the material for analysis is an imperative necessity.
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| 10. |
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