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Nordstoga, K; Ytrehus, B; Christophersen, Bjørn & Olivecrona, G
(2007).
Mesenteric Chylothrombosis in Hyperlipidaemic Mink.
Journal of Veterinary Medicine A.
ISSN 0931-184X.
54,
s. 1–3.
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Sæther, Thomas; Tran, Thien Ngoc; Christophersen, Bjørn & Haugen, Trine Berit
(2002).
Effect of Dietary Fats, Insulin and Dexamethasone on delta6-desaturase Expression in Rat Testis.
Vis sammendrag
The testis is an extraordinary organ regarding the fatty acid metabolism. Although rich in polyunsaturated fatty acids (PUFAs), the testis is continuously drained of these fatty acids, as the spermatozoa are transferred to the epididymis. This makes a great contrast to other PUFA-rich tissues like the brain and retina. In all cells the dietary essential fatty acids; linoleic acid (18:2(n-6)) and linolenic acid (18:3(n-3)) are converted to the important fatty acids 22:5(n-6) and 22:6(n-3) by alternating steps of elongation and desaturation. The delta6-desaturase catalyses a rate-limiting step in this conversion. Germ cells are especially rich in PUFAs, more than the Sertoli cells, but Sertoli cells seem to be more active in converting the dietary essential fatty acids to 22:5(n-6) and 22:6(n-3), than germ cells are. We have recently showed that delta6-desaturase is regulated differently in the testis that in liver in response to essential fatty acid deficiency (EFAD), induced by a fat free diet. In liver delta6-desaturase expression is upregulated in response to EFAD, while in testis no such increase is observed. This may be explained by differences in the expression pattern of the PPARs (peroxisome proliferating activated receptors) in liver and testis, a nuclear receptor family governing the fatty acid metabolism. Both dexamethasone and insulin induce an upregulation of the delta6-desaturase expression in the Sertoli cells. The induction is more rapid with dexamethasone than with insulin. When stimulating Sertoli cell cultures with arachidonic acid in combination with dexamethasone and insulin respectivly, only a very small drop in delta6-desaturase expression is observed. Arachidonic acid is known to bind to PPAR-alpha as a ligand, and in tissues like the liver, induce a marked downregulation of the delta6-desaturase expression. This difference in response to arachidonic acid can partly explain the results seen in the feeding experiment.
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Sæther, Thomas; Tran, Thien Ngoc; Christophersen, Bjørn & Haugen, Trine Berit
(2002).
Effect of Dietary Fats, Insulin and Dexamethasone on delta6-desaturase Expression in Rat Testis.
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Sæther, Thomas; Tran, Thien Ngoc; Christophersen, Bjørn & Haugen, Trine Berit
(2001).
Effect of Dietary Fats, Insulin and Dexamethasone on delta6-desaturase Expression in Rat Testis.
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Sæther, Trond; Tran, Thien Ngoc; Christophersen, Bjørn & Haugen, T. B.
(2001).
Effect of dietary fats, insulin and dexamethasone on - desaturase expresion in rat testis.
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Tran, Thien Ngoc; Sæther, Thomas; Christophersen, Bjørn; Rootwelt, Helge; Retterstøl, Kjetil & Haugen, Trine Berit
(2001).
Expression of delta6- and delta5-desaturase in Rat Testis.
Vis sammendrag
Previous studies have shown that rat fed diets deficient in essential fatty acids show testicular atrophy and become infertile. This was not prevented by the inclusion of linolenic acid (18:3n-3), but the testicular development was normal when the diet was supplemented with linoleic acid (18:2n-6). In most animal cells 22:6(n-3) is the major 22-carbon polyunsaturated fatty acid in the membrane lipids, whereas rat testis contains more 22:5(n-6) than 22:6(n-3). The amount of 22:5(n-6) increases from 2 to 20% of total fatty acids in the progression of germ cell differentiation from spermatogonia to condensing spermatids, and this level is higher than in Sertoli cells. The linolenic acid and linoleic acid are converted to 22:6(n-3) and 22:5(n-6) by alternating sequences of elongation and desaturation. The delta6-desaturase catalyzes a rate-limiting step in the conversion of 18:3(n-3) and18:2(n-6) to 18:4(n-3) and 18:3(n-6), respectively, whereas the rate of desaturation of 20:4(n-3) and 20:3(n-6) is determined by the activity of delta5-desaturase. This study demonstrates the expression of both delta5- and delta6-desaturase mRNA in rat testis. The levels of the transcripts were high in Sertoli cells, whereas only weak signals were observed in the germ cell fractions. The results are consistent with previous report that Sertoli cells were more active to convert 18:2(n-6) and 20:4(n-6) to 22:5(n-6) than germ cells and support the hypothesis that biosynthesized C22:5(n-6) from Sertoli cells can be transferred to developing germ cells. Furthermore, our results suggest that the regulation of the desaturases is different in liver and testis.
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Tran, Thien Ngoc & Christophersen, Bjørn
(2001).
Oxidation of polyunsaturated fatty acids in isolated rat hepatocytes and the metabolic fate of released acetate.
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Tran, Thien Ngoc & Christophersen, Bjørn
(2001).
The transport of acetyl units released from peroxisomal fatty acid oxidation to mitochondria in isolated rat hepatocytes.
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Tran, Thien Ngoc & Christophersen, Bjørn
(2001).
Oxidation of polyunsaturated fatty acids in isolated hepatocytes and the metabolic fate of acetate released by peroxisomal fatty acid oxidation.
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Christophersen, Bjørn
(2000).
Laurell deler sine kunnskaper om plasmaproteinelektroforeser med oss.
Klinisk Biokemi i Norden.
ISSN 1101-2013.
12(4).
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Retterstøl, Kjetil; Haugen, Trine Berit; Tran, Thien Ngoc & Christophersen, Bjørn
(2000).
A study of the metabolism of N-9, N-6 and N-3 fatty acids in cells from immature rat testes and from adult human testes.
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Tran, Thien Ngoc; Christophersen, Bjørn; Rootwelt, Helge; Retterstøl, Kjetil & Haugen, Trine Berit
(2000).
Expression of _D6-desaturases in rat testes.
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Christophersen, Bjørn
(2000).
Klinisk-kjemiske risikoparametre i vurdering av høyrisikopasienter (CRP, Lp(a)).
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Retterstøl, Kjetil; Haugen, Trine Berit & Christophersen, Bjørn
(1999).
Lange flerumettede fettsyrer kan ha betydning for mannlig reproduksjonsevne.
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Christophersen, Bjørn & Brun, Atle
(1999).
Transferrin reseptor (TfR), biosyntese og analyse av løselig reseptor.
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Retterstøl, Kjetil; Haugen, T. B. & Christophersen, Bjørn
(1999).
Lange flerumettede fettsyrer kan ha betydning for mannlig reproduksjonsevne. Resultater fra våre studier omkring syntesen og metabolismen av slike fettsyrer.
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Tran, Thien Ngoc; Retterstøl, Kjetil & Christophersen, Bjørn
(1999).
Regulation of metabolism of 22:4(n-6) and 22:5(n-3) to 22:5(n-6) and 22:6(n-3) in isolated rat hepatocytes.
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Retterstøl, Kjetil; Haugen, Trine Berit; Pran, T N. & Christophersen, Bjørn
(1999).
The pathway from arachidonic to decosapentaenoic acid (22:5n-6) and from eicosapentaenoic to docosahexaenoic acid (22:6n-3) studied in rat testicular cell.
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Christophersen, Bjørn; Olivecrona, Gunilla & Nordstoga, Knut
(1999).
Lipoprotein lipase deficiency with pancreatitis studied in an animal model.
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Retterstøl, Kjetil; Røkkum, Magne & Christophersen, Bjørn
(1999).
Does the apolipoprotein E genotype influence on the nerve growth of nevroms in humans?
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Retterstøl, Kjetil; Haugen, Trine Berit; Tran, Thien Ngoc & Christophersen, Bjørn
(1999).
The pathway from arachidonic to docosapentaenoic acid (22:5n-6) and from eicosapentaenoic to docosahexaenoic acid (22:6n-3) studied in rat testicular cells.
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Retterstøl, Kjetil; Christophersen, Bjørn & Haugen, Trine Berit
(1997).
Elongation and Desaturation of n-3,n-6 and n-9 Fatty Acids and Synthesis of C24 Intermediates in Rat Testicular Cells.
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Retterstøl, Kjetil; Christophersen, Bjørn & Haugen, Trine Berit
(1997).
Elongation and Desaturation of n-3, n-6 and n-9 Fatty Acids and Synthesis of C24 Intermediates in Rat Testicular cells.
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Haugen, Trine Berit; Retterstøl, Kjetil & Christophersen, Bjørn
(1997).
The metabolism of long chain polyunsaturated fatty acids in rat testicular cells.
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Haugen, Trine Berit; Retterstøl, Kjetil & Christophersen, Bjørn
(1997).
The metabolism of long chain polyunsaturated fatty acids in rat testicular cells.
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Haugen, T. B.; Retterstøl, Kjetil & Christophersen, Bjørn
(1997).
The metabolism of long chain polyunsaturated fatty acids in rat testicular cells.
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Haugen, T. B.; Retterstøl, Kjetil & Christophersen, Bjørn
(1997).
The metabolism of long chain polyunsaturated fatty acids in rat testicular cells.
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Retterstøl, Kjetil; Haugen, T. B. & Christophersen, Bjørn
(1997).
Metabolism of long chain polyunsaturated fatty acids in rat testis cells.
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Savonen, Roger; Nordstoga, Knut; Christophersen, Bjørn; Hultin, Magnus; Olivecrona, Thomas & Olivecrona, Gunilla
(1997).
Chylomicron metabolism in type 1 hypertriglyceridemic mink (Mustela vison).
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Rootwelt, Helge & Christophersen, Bjørn
(1999).
"Er dette lymfe"?
Rikshospitalet, Oslo..
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Christophersen, Bjørn
(1999).
Transferrinreseptor.
Rikshospitalet, Oslo.