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- Alexson, Stefan E. H., 1953-
(author)
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Peroxisomal and mitochondrial fatty acid metabolism in brown adipose tissue and liver
- 1985
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Doctoral thesis (other academic/artistic)abstract
- Brown adipose tissue (BAT) produces heat in response to cold. The heat produced is mainly due to oxidation of fatty acids. In animal tissues, fatty acid 9-oxidation has generally been assumed to occur in mitochondria. The discovery of a 9-oxidation system in rat liver peroxisomes raised questions as to whether a similar system is present in BAT (a tissue with very active fatty acid metabolism) and what the physiological significance of such a system would be in heat production. BAT has very high activity of mitochondrial 9-oxidation enzymes, but nonetheless the results showed that BAT also contains peroxisomes with a 9-oxidation activity. The peroxisomal fatty acid capacity is increased several-fold during acclimation to cold. However, in spite of this pronounced increase, peroxisomes were found to contribute only 5-10% to overall cellular fatty acid oxidation.When substrate specificities were studied for the two systems, they showed qualitative differences. Peroxisomes preferentially oxidised medium- -chain fatty acids, and showed highest affinity towards medium-chain and long-chain unsaturated fatty acids, whereas mitochondria showed highest oxidation rates and affinity with long-chain saturated fatty acids.BAT peroxisomal 9-oxidation enzymes were identified by antibodies raised against the corresponding rat liver peroxisomal enzymes. Acyl-CoA oxidase (the rate-limiting enzyme of peroxisomal 9-oxidation) was found to increase selectively, thus causing the increase in peroxisomal 9-oxidation capacity. Both peroxisomal and mitochondrial 9-oxidation enzymes were found to increase also in liver in rats exposed to cold. However, these increases may primarily be a response to an increased caloric intake.The intraparticulate localization of various enzymes was investigated in rat liver peroxisomes. The data suggest that the peroxisomal matrix contains some poorly soluble enzymes that may form a matrix structure.Mitochondrial 9-oxidation in BAT was found to be sensitive to eru- coyl-carnitine. When the mechanism for the inhibition was studied, the inhibition was found to be due to sequestration of CoA, thus all CoA- -dependent substrates were found to be inhibited to an extent which was correlated to the intramitochondrial level of free CoA.Three different acyl-CoA hydrolases with very high activities were found in rat and hamster BAT. The hydrolases were found to have different substrate specificities and a complex regulation by ADP, NADH and ions. These data suggest that the acyl-CoA hydrolases have an important function in BAT fatty acid metabolism.The results presented here show that BAT contains cold-inducible 9-oxidation systems in both peroxisomes and mitochondria. The marked proliferation of peroxisomes in BAT differs from drug-induced peroxisome proliferation and brown adipose tissue may thus be an interesting tissue in which to study peroxisome proliferation in response to physiological stimuli.
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| 2. |
- Andersson-Engels, Stefan, et al.
(author)
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Autofluorescence of various rodent tissues and human skin tumour samples
- 1987
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In: Lasers in Medical Science. - 0268-8921. ; 2:1, s. 41-49
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Journal article (peer-reviewed)abstract
- Fluorescence spectra from different organs in rats and mice have been recorded to explore the potential of non-intrusive tissue diagnostics. The fluorescence was induced by a nitrogen laser that emitted at a wavelength of 337 nm. Optical multichannel techniques were used for the detection. Spectra are given from 19 different sites in Wistar/Furth rats, including an inoculated malignant tumour. The spectra seem to be a sum of two wavelength distributions only, each distribution occurring with a different weight in different organs. Spectra obtained from living and dead tissue were compared to verify that the measurements on sacrificed experimental animals were valid. Preliminary results are given for some human tumours, transplanted in nude mice, and for some human skin samples.
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| 3. |
- Andersson-Engels, Stefan, et al.
(author)
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Identification of brain tumours in rats using laser-induced fluorescence and haematoporphyrin derivative
- 1989
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In: Lasers in Medical Science. - 0268-8921. ; 4:4, s. 241-249
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Journal article (peer-reviewed)abstract
- Laser-induced fluorescence has been used for the identification of brain tumours in rats, which have been previously given tumour-seeking haematoporphyrin derivative. A pulsed nitrogen laser (λ=337 nm) was used in conjunction with an optical multichannel analyzer. For both inoculated RG-2 and TCVC rat-brain-tumour models, the blue autofluorescence was strongly reduced in the tumour compared with normal brain tissue, and at the same time the characteristic red-drug signal increased. The contrast between tumour and normal tissue was strongly enhanced by forming the ratio between the two signals. Implications for possible improvement of tumour delineation in brain tumour surgery are discussed.
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| 8. |
- Lohmander, Stefan, et al.
(author)
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Post-translational events in proteoglycan synthesis : Kinetics of synthesis of chondroitin sulfate and oligosaccharides on the core protein
- 1986
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In: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861. ; 250:1, s. 211-227
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Journal article (peer-reviewed)abstract
- Chondrocytes isolated from the Swarm rat chondrosarcoma were incubated in culture with [1-3H]glucose for 30 min to 8 h. Labeled proteoglycans were isolated, treated with borohydride under alkaline conditions, and the three complex sugar structures purified: N- and O-linked oligosaccharides and chondroitin sulfate chains. The amount of incorporated radioactivity into each component sugar was analyzed by HPLC after enzyme digestion and hydrolysis. The kinetic data for labeling of each sugar over the time course of the experiment were fit to first-order rate equations and the half times (t 1 2) to linear labeling were calculated. The t 1 2 values were essentially the same, 5-8 min, for galactose in all three complex sugar structures and for chain glucuronic acid in chondroitin sulfate, while that for xylitol in chondroitin sulfate, 15.8 min, was significantly longer. Thus, oligosaccharide synthesis is concomitant with chondroitin sulfate chain synthesis; the addition of the chondroitin sulfate linkage galactose occurs at or nearly at the same time as chain elongation while the addition of linkage xylose residues to the core protein may precede chain synthesis by up to 8 min. Since the intracellular t 1 2 of the core protein precursor for these cells is 45 to 90 min, the data strongly suggest that the addition of xylose is not completed to any significant extent while the polypeptide is still nascent or shortly after its release into the rough endoplasmic reticulum. It is proposed that the addition of xylose to the core protein precursor is a late endoplasmic reticulum or early Golgi event. The analytical data were consistent with the presence of ester phosphate on about 80% of the xylose residues of the newly synthesized proteoglycan.
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| 9. |
- Olsson, L E, et al.
(author)
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Ferrous sulphate gels for determination of absorbed dose distributions using MRI technique : basic studies
- 1989
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In: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 34:1, s. 43-52
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Journal article (peer-reviewed)abstract
- Two gels have been found to be suitable to load with ferrous sulphate solution. In these soft tissue equivalent phantoms, the absorbed dose distribution can be measured after irradiation in clinically used MR imaging equipment. The present studies were carried out using a 0.25 T NMR analyser without imaging properties. A ferrous sulphate solution, 0.05 M with respect to sulphuric acid, can be gelled with 4% gelatin to give a dosemeter which has a response which is linearly correlated (r = 0.998) with the absorbed dose in the interval 0-40 Gy. Ferrous sulphate solution can also be gelled with 1% agarose, but this gel has to be purged with oxygen to obtain a linear relationship (r = 0.997) in the same absorbed dose interval. The ferrous sulphate loaded gels have a sensitivity which is a factor of 2.2 or 4.0 times higher for gelatin and agarose, respectively, than the ordinary dosemeter solution. Because the standard deviation of background measurements is higher for the gels than for the dosemeter solution, the minimum detectable absorbed dose is about the same, or 1.0 Gy, for the two gels and the dosemeter solution. The sensitivity of the ferrous sulphate loaded gels shows no dependence on dose rate if the mean dose rate and the absorbed dose per pulse are within the limits normally used by accelerators for radiotherapy.
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| 10. |
- Weisner, Stefan E.B. 1954-
(author)
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Factors affecting the internal oxygen supply of Phragmites australis (Cav.) Trin. ex Steudel in situ
- 1988
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In: Aquatic Botany. - Amsterdam : Elsevier. - 0304-3770 .- 1879-1522. ; 31:3-4, s. 329-335
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Journal article (peer-reviewed)abstract
- Oxygen concentration in basal stems of Phragmites australis (Cav.) Trin. ex Steudel was measured in situ, in monospecific stands. The mean O2 concentration in basal stems, and mean shoot length above water, decreased in deeper water. Oxygen concentration in basal stems was correlated to shoot length above water at a given water depth, and the mean O2 concentration in basal stems of shoots with similar length above water decreased in deeper water. The results suggest that O2 transport from shoots to below-ground parts is restricted in deep water by: (1) small shoot length above water; (2) long O2 transport distance. No influence of substrate redox potential on O2concentration in basal stems was found. © Copyright 1988 Elsevier B.V.
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