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| 2. |
- Alm, Gunnar V., et al.
(författare)
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The in vitro maturation of the embryonic chicken thymus, 1: : Development of an Organ Culture System
- 1972
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Ingår i: Acta Pathologica Microbiologica Scandinavica, Section A Pathology. - : Wiley. - 0365-4184. ; A 80:6, s. 778-784
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Tidskriftsartikel (refereegranskat)abstract
- An organ culture technique is described which permits the lymphoid development of the thymic anlagen of 10-day-old chick embryos for at least 10 days in vitro. Grid organ cultures of a modified Trowell type were employed. Among several tissue culture media tested, Waymouth's MB 752/1 medium gave superior results. In initial experiments this medium was supplemented with heat-inactivated horse serum and embryo-extract. Subsequently it was found that this supplement could be substituted for by chicken serum alone. The morphological development of the embryonic thymic anlagen in organ culture has been characterized. Typical lymphoid cells developed from the initial lymphoid precursor cells. Late in the culture period, large numbers of small lymphocytes appeared. Extensive cell proliferation was demonstrated during the first 6 days of culture by means of autoradiography. This organ culture technique should facilitate the further analysis of factors influencing thymic lymphocytopoiesis as well as of the role of the thymus in the development of lymphocyte functions.
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| 3. |
- Berg, B., et al.
(författare)
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Fungal biomass and nitrogen in decomposing scots pine needle litter
- 1979
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Ingår i: Soil Biology & Biochemistry. - 0038-0717. ; 11:4, s. 339-341
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Tidskriftsartikel (refereegranskat)abstract
- The development of fungal biomass and increase of amounts of N was studied in decomposing pine needle litter for about 3 yr. After a relatively rapid increase of the amount of mycelium the fungal biomass became rather constant after about 2 yr. The absolute amount of N in the needles increased between the 4th and the 16th months and this increase was correlated to the increase of fungal biomass in the needles.
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| 4. |
- Björn, G S, et al.
(författare)
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Action spectra for conversions of phycochrome c from Nostoc-muscorum
- 1978
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 43:3, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- The reversibly photochromic pigment, phycochrome c, was extracted from the blue-green alga Nostoc muscorum strain A. Action spectra were determined for in vitro conversions of the pigment from the short wavelength to the long wavelength form and vice versa. The action peak for the absorbance decrease at 650 nm is at 630 nm. During this decrease there is only a slight increase of the absorbance in the green region. Green and yellow light (maximum efficiency at 580 nm) completely restores absorbance at 650 nm. The observations are explained by the existence of three spectrally different forms of phycochrome c: Pc630 and Pc650 which equilibrate in darkness and Pc580 which is reversibly photoconvertible to Pc630. We have also measured the absorbance changes brought about by saturating irradiations with light of various wavelengths ("photostationary state spectrum"). Extreme photostationary states were obtained with about 650 nm and 500 nm light.
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| 5. |
- Björn, G S, et al.
(författare)
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Photochromic pigments from blue-green algae - phycochrome-A, phycochrome-B and phycochrome-C
- 1976
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 36:4, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous extracts of blue-green algae were fractionated by electrofocusing. In all algae investigated, fractions with isoelectric points at or near 4.6 showed photochromic behavior analogous to that of phytochrome, although they were sensitive to light of shorter wavelength. Three main types of photochromic pigments were found. Phycochrome a (in Tolypothrix distorta, Phormidium luridium, Nostoc muscorum 1453/12 and Anacystis nidulans) had 1 form absorbing maximally at about 590 nm (formed under red light) and 1 absorbing maximally at about 630 nm (formed under green light). Phycochrome b (in T. distorta) had 1 form absorbing maximally near 510 nm and 1 form absorbing maximally at 570 nm (formed in yellow-green and blue-green light, respectively). Phycochrome c (in N. muscorum A and probably in T. tenuis) had 1 form absorbing maximally at 650 nm (formed under green light) and 1 absorbing very weakly in the green region (formed under red light). The conversion of Phormidium phycochrome a from its red-absorbing form to its green-absorbing form caused the same spectral change as if an f-chromophore of phycocyanin were transformed into an s-chromophore. The quantum yield for this conversion was estimated to be 0.1, while the quantum yield for the reversion was estimated to be 0.4 on the assumption that the absorption coefficients were those of f- and s-chromophores. Phycochrome c was less light-sensitive than phycochromes a and b.
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| 6. |
- Björn, Lars Olof, et al.
(författare)
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Imaging by delayed light-emission (phytoluminography) as a method for detecting damage to the photosynthetic system
- 1979
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 47:4, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- An improved apparatus for obtaining luminescence (delayed light emission) images of plants is described. It consists of a phosphoroscope equipped with an imaging lens and an electronic image intensifier. It is also equipped with light-sources for obtaining images with reflected light and fluorescence light. Damage to the photosynthetic system caused by virus, insects, high or low temperature, UV radiation, or herbicide, and also chloroplast senescence as part of a normal developmental process, can be followed by this non-destructive method. In many cases changes which are not visible in fluorescence images are clearly seen in luminescence images. (Leaves of Hibiscus sp., Oxalis tetraphylla, Nicotiana glutinosa with a tobacco mosaic virus infection, Fagus sylvatica with midge gall and Polypodium vulgare were used.).
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| 7. |
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| 8. |
- Björn, Lars Olof
(författare)
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State of protochlorophyll and chlorophyll in corn roots
- 1976
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317. ; 37:3, s. 183-184
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Tidskriftsartikel (refereegranskat)abstract
- The protochlorophyll(ide) present in primary roots of dark-grown corn (Zea mays) seedlings has an in vivo absorption maximum at 634 nm. Red light converts the pigment to chlorophyll(ide) a with an absorption maximum at 675 nm.
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| 9. |
- Björn, Lars Olof
(författare)
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Why are plants green - relationships between pigment absorption and photosynthetic efficiency
- 1976
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Ingår i: Photosynthetica. - 0300-3604. ; 10:2, s. 121-129
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Tidskriftsartikel (refereegranskat)abstract
- The maximum efficiency of an optically thin photosynthetic system in converting solar radiation into chemical energy is theoretically considered as a function of the absorption spectrum of the photon-collecting pigment. The absorption band position giving maximum rate of power conversion is close to 700 nm in full sunlight and at somewhat shorter wavelength in weaker light. The chemical potential obtainable is decreased if the band is too wide. The effect of a 2nd absorption band (or accessory pigment) on potential is rather small.
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| 10. |
- Blomquist, G., et al.
(författare)
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Classification of fungi by means of pyrolysis-gas chromatography pattern recognition
- 1979
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 173:1, s. 19-32
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Tidskriftsartikel (refereegranskat)abstract
- SUMMARY Repetitive samples of three strains of the moujd Penicillium were subjected to pyrolysis-gas chromatography (Py-GC). From the chromatograms, 26 peak heights were used in a subsequent SIMCA pattern recognition analysis. This data analysis gives a marked improvement in the classification of the samples (100% correct, 85% unique) in comparison with the traditional analysis based on the average chromatogram of each class (92% correct, 45% unique)_ The data analytical method is described in detail using the Py-GC data as an illustration.
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