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A Jacobsson

Publications and source records attributed to A Jacobsson.

36 records · Page 2Linked to original sources
PubMed1994

The uncoupling protein thermogenin during acclimation: indications for pretranslational control.

To analyze the regulation of the content of the uncoupling protein thermogenin in brown adipose tissue, we have selected a physiological transition phase during which to investigate the relationship between the level of mRNA and the level of the ensuing protein product. Mice preacclimated to 28 degrees C were transferred to 4 degrees C. Cold acclimation led to the expected increases in brown fat total protein and RNA content. Two recruited proteins were analyzed: the cytosolic glycerol-3-phosphate dehydrogenase and the mitochondrial uncoupling protein thermogenin. The activity of the dehydrogenase acutely followed the level of the corresponding mRNA, indicating pretranslational control. However, for thermogenin there was a marked time delay between the establishment of the fully recruited level of thermogenin mRNA (after only approximately 4 h of cold exposure) and that of thermogenin itself (after > 3 wk). By reiterative computer simulation, it was investigated whether a model only involving pretranslational regulation could be invoked for either system. For glycerol-phosphate dehydrogenase, a plausible model could be constructed, provided the protein half-life was shorter than approximately 24 h. Despite the long time delay between full thermogenin mRNA recruitment and full thermogenin protein recruitment, a plausible pretranslational control model could also be constructed, provided that the protein half-life was approximately 5 days. This computed value was in good agreement with the half-life obtained from independent thermogenin half-life studies. It is implied that pretranslational control may suffice to explain the regulation of thermogenin content in brown adipose tissue during a warm-to-cold transition period.

Acclimatization↗
PubMed1993

Differential adrenergic regulation of C/EBP alpha and C/EBP beta in brown adipose tissue.

We investigated the regulation of the expression of two members of the C/EBP family of transcriptional activators, C/EBP alpha and C/EBP beta, in brown adipose tissue in mice. Less than one hour of cold exposure led to dramatic changes in the expression of both genes. C/EBP alpha steady-state mRNA and protein levels were drastically and rapidly reduced whereas C/EBP beta mRNA and protein levels were induced severalfold. Also norepinephrine injection affected the expression of the transcription factors. Preconfluent cells in brown fat primary cultures responded to norepinephrine with a decrease in C/EBP alpha and an increase in C/EBP beta mRNA; in confluent cells the expression of both factors was increased. Thus, C/EBP alpha and C/EBP beta gene expression is under adrenergic control both in vivo and in vitro but the type of response is directed by the degree of differentiation of the cells.

Adipose Tissue, Brown↗
PubMed1992

Alterations of glycosphingolipid-based blood group antigen expression on erythrocytes and in plasma studied on consecutive samples after a blood group O to A bone marrow transplantation.

A blood group A1Le(a-b+) individual with chronic myeloid leukaemia had received a bone marrow graft from an HLA-identical OLe(a+b-) donor. Twelve months after bone marrow transplantation (BMT), the red blood cells of the patient became agglutinable with anti-A blood group reagents. To elucidate whether the blood group A antigen expression was of plasma or of bone marrow origin, total non-acid glycosphingolipid fractions were prepared from red blood cells and plasma collected 17 months after BMT, and from plasma collected 13, 15 and 19 weeks after BMT. The glycolipid fractions were analysed by thin-layer chromatography and immunostained with monoclonal A-antibodies, and permethylated and permethylated-reduced derivatives of selected plasma samples were analysed by mass spectrometry. The results strongly indicate the presence of host bone marrow-produced blood group A red blood cells. Furthermore, the presence of a blood group H active pentaglycosylceramide type 1 (H-5-1) (Table I), characteristic for an OLe(a-b-) secretor, was seen in plasma 3-4 weeks before clinical chronic graft versus host disease (GVHD). After treatment of chronic GVHD, this expression disappeared. The blood group ALeb (A-7-1) antigen produced by the recipient seems to be present and to increase with time in all plasma samples. This also seems to be the case for the Leb and A-6-1 antigens.

ABO Blood-Group System↗
PubMed1992

Regulation of expression of the lipoprotein lipase gene in brown adipose tissue.

The regulation of lipoprotein lipase gene expression in brown adipose tissue was studied. Rats were preacclimated to 21 degrees C. Exposure to cold (4 degrees C) resulted in a rapid increase in the level of lipoprotein lipase mRNA in the tissue. The level peaked (expressed per microgram total RNA) after approximately 8 h and then slowly declined. The increased lipoprotein lipase mRNA level was not due to an increased stability of the mRNA, but, in a transition event from a high to a low expression of the lipoprotein lipase gene, a transcription-dependent process was recruited that accelerated the breakdown of lipoprotein lipase mRNA. Norepinephrine injections increased lipoprotein lipase mRNA levels in the tissue; this effect was mediated via a beta-adrenergic receptor. The effect of cold could be mimicked by norepinephrine injections, and these two effects were not additive, indicating that the cold effect was mediated by norepinephrine. The lipoprotein lipase mRNA level was also increased by insulin injections (into fasted animals); thus an increase in lipoprotein lipase gene expression in brown adipose tissue may be induced via two different stimuli, which, intracellularly, would be mediated via different signaling systems. In all investigated conditions, the changes in lipoprotein lipase mRNA levels observed here were parallelled by alterations in lipoprotein lipase activity reported earlier from this laboratory. It was therefore concluded that, under the conditions studied, lipoprotein lipase activity in brown adipose tissue was primarily regulated at the transcriptional level.

Adipose Tissue, Brown↗
PubMed1990

Glycolipid- and glycoprotein-based blood group A antigen expression in human thrombocytes. A1/A2 difference.

Total non-acid glycolipid fractions and total sodium dodecylsulphate (SDS) solubilized protein fractions were isolated from human thrombocytes obtained from single human donors having different blood group A1/A2 phenotypes. The blood group A glycolipid antigens were characterized by immunostaining of thin layer plates with different monoclonal anti-A antibodies. The glycoproteins carrying blood group A epitopes were identified by SDS-PAGE and Western blot analysis using a monoclonal anti-A antibody. Blood group A glycolipid antigens were found in both A1 and A2 thrombocytes but the A2 individuals expressed at least ten times less A glycolipids compared to the A1 individuals. Expression of A type 3/4 chain and small amounts of A type 1 chain glycolipids were seen in thrombocytes of both A1 and A2 individuals, while the type 2 chain A glycolipids appeared to be missing from the A2 thrombocytes. Blood group A reactive glycoproteins were only found in thrombocytes of A1 individuals and could not be detected in A2 individuals or a blood group O individual. The major blood group A glycoprotein were found as a double band migrating in the 130 kDa region.

ABO Blood-Group System↗
PubMed1990

Blood group A glycolipid antigen biosynthesis: discrimination between biosynthesized and enzyme preparation derived blood group A antigen by mass spectrometry.

A monofucosyl type 1 chain blood group A hexaglycosylceramide was biosynthesized in solution using the type 1 chain blood group H pentaglycosylceramide as precursor, a crude microsomal fraction prepared from the mucosa scraping of a blood group A pig small intestine as enzyme source, and uridine diphosphate-N-acetyl-(1-14C)galactosamine as sugar donor. The radioactive product was enriched using reversed-phase column chromatography and silica gel HPLC. The peak, as detected by a beta-flow scintillation counter, was collected, permethylated, and analyzed by mass spectrometry. Carbohydrate sequence ions were found, indicating the presence of both the biosynthesized and a native, non-14C-containing blood group A hexaglycosylceramide. The blood group A pig small intestinal mucosa used as the enzyme source contain blood group A hexaglycosylceramide as the predominant glycolipid. Therefore, it is concluded that the nonradioactive blood group A hexaglycosylceramide found after the biosynthesis is derived from the enzyme preparation.

ABO Blood-Group System↗
PubMed1990

Determination of prostate-specific antigen in serum by immunoradiometric assay.

A better understanding is needed of the role of pre-analytical factors if prostate-specific antigen (PSA) is to be reliably used as a tumor marker. Reports on the analytical performance of TANDEM-R PSA (Hybritech, Inc., San Diego, CA) differ considerably with respect to detection limit and imprecision, differences that might be due (e.g.) to the use of different control matrices, to between-batch variations in reagent composition, or to nonrobustness of the assay. During nine months we determined PSA in 986 serum samples from 728 male urology patients and 54 samples from women (25 assay runs). As controls we used two serum pools with low PSA concentration and two widely used commercial controls. The within-assay CV for patients' samples was similar to that found with the commercial controls: 2.6% to 3.4% in the upper part of the normal reference interval. Precision was worse at lower concentrations (CVs 5-10% at about 0.5 micrograms/L). Imprecision tended to be higher at the end of runs. Assay drift for 100-tube runs was -4%. PSA was stable at -20 degrees C during six months. Neither the polyester polymer in SST tubes nor a hemolysate had any detectable effect on PSA values. Clinical analysis of the first 322 patients and all patients with PSA less than or equal to 0.20 micrograms/L highlighted the requirements for strict adherence to sampling instructions and to stringent quality control also at low analyte concentrations (analyte-free sera and sera with PSA concentrations 0.2-0.5 micrograms/L). Values with TANDEM-R PSA and IRMA-Count PSA (Diagnostic Products Corp., Los Angeles, CA) correlated well with no difference in detection limit or with samples from women. Within-assay precision was better with IRMA-Count PSA in the upper part of the normal reference interval and above. The designs of the two assays were compared in a format that is generally applicable for immunoassay kits (NORDKEM kit group, unpublished), and subjective impressions were recorded.

Analysis of Variance↗
PubMed1989

Postnatal recruitment of brown adipose tissue is induced by the cold stress experienced by the pups. An analysis of mRNA levels for thermogenin and lipoprotein lipase.

In order to investigate the postnatal recruitment process, gene expression in the brown adipose tissue of rat pups was followed during the first 20 h of life. In normal pups, the level of mRNA coding for the uncoupling protein thermogenin increased markedly but gradually within the first 24 h. Lipoprotein lipase and actin mRNA levels were relatively low and remained constant. In pups exposed to thermoneutral temperature (35 degrees C) for the first 12 h after birth, no increase in thermogenin mRNA or lipoprotein lipase mRNA was observed, whereas in pups exposed to 28 degrees C a clear increase in both thermogenin and lipoprotein lipase mRNA levels was found. Actin mRNA levels were not affected by the environmental temperature under these circumstances. It was concluded that the postnatal recruitment in brown adipose tissue is a consequence of the cold stress experienced by the newborn pups. Thus, postnatal recruitment is not ontogenically predetermined.

Actins↗
PubMed1989

Brown adipocytes differentiated in vitro can express the gene for the uncoupling protein thermogenin: effects of hypothyroidism and norepinephrine.

Expression of the gene for the brown-fat specific uncoupling protein thermogenin was investigated in cell cultures by hybridization of isolated RNA with a cDNA clone corresponding to mouse thermogenin. The RNA was isolated 3-4 days after confluence from cells differentiated in culture from precursors isolated from the interscapular brown adipose tissue of 5-week-old mice. Very low thermogenin mRNA levels were found in cells derived from untreated mice, and there was only little effect of added norepinephrine on thermogenin gene expression in these cells. However, in cells derived from hypothyroid (methimazole-treated) mice there was a higher expression of thermogenin, and norepinephrine had a marked augmenting effect on the thermogenin mRNA level in these cells. These effects of thermogenin mRNA levels were specific, in that they contrasted with the effects of hypothyroidism and norepinephrine on the level of other mRNA species in these cells (coding for beta-actin, lipoprotein lipase, cytochrome-c oxidase, and glycerol-3-phosphate dehydrogenase). It was concluded that brown-fat cells in culture can reach a differentiated state, sufficiently advanced that the unique properties of these cells can be expressed, and that thermogenin gene expression (i.e., the level of thermogenin mRNA) is under direct control of norepinephrine.

Actins↗
PubMed1987

Physiological activation of brown adipose tissue destabilizes thermogenin mRNA.

The amount of mRNA coding for the brown fat specific uncoupling protein thermogenin was followed in the brown adipose tissue of adult mice. As expected, cold exposure or norepinephrine injection caused an increase in the amount of thermogenin mRNA. However, contrary to expectation, the half-life of thermogenin mRNA was dramatically reduced, from about 18 h to about 3 h, when the mice were cold exposed. This destabilization of thermogenin mRNA was not related to the activity of protein synthesis. It was concluded that in brown adipose tissue an unusual mechanism operates which leads to a destabilization of thermogenin mRNA under the same physiological conditions which increase thermogenin gene expression.

Acclimatization↗
PubMed1987

Euthyroid status is essential for the perinatal increase in thermogenin mRNA in brown adipose tissue of rat pups.

The amount of mRNA coding for the brown-fat specific, uncoupling protein thermogenin was followed perinatally in fetuses and newborns from normal and hypothyroid rat dams. Although the growth of the fetuses and newborns was normal in the hypothyroid group, they had a lower amount of thermogenin mRNA already in-utero, and the dramatic postnatal increase in thermogenin mRNA was nearly completely abolished. It is concluded that the euthyroid state is essential for the regulation of the expression of the thermogenin gene.

Adipose Tissue, Brown↗
PubMed1986

alpha- and beta-adrenergic control of thermogenin mRNA expression in brown adipose tissue.

By the use of an earlier characterised cDNA clone, CIN-1, corresponding to a sequence of the mRNA coding for the brown-fat specific "uncoupling" protein, thermogenin, the amount of thermogenin mRNA found in the brown adipose tissue of mice was quantitatively investigated under different physiological and pharmacological conditions. It was found that a 4 hr cold stress led to a 7-fold increase in the amount of thermogenin mRNA; injection of norepinephrine had a significant but smaller effect. Most notably, isoprenaline (beta-agonist) and phenylephrine (alpha-agonist) had in themselves no effect, but when injected together were able to increase the mRNA level synergistically. In 4 hr cold-stressed mice, norepinephrine, isoprenaline and cholera toxin could all further potentiate the effect of the cold stress itself on the mRNA level. Insulin and the glucocorticoid dexamethasone both had weak stimulatory effects on the mRNA level. It is concluded that an increase in intracellular cAMP levels is a necessary and perhaps sufficient stimulus for the increase in thermogenin gene expression. However, at least under in vivo conditions, this increase requires stimulation of both alpha- and beta-adrenergic pathways.

Adipose Tissue, Brown↗
PubMed1985

Mitochondrial uncoupling protein from mouse brown fat. Molecular cloning, genetic mapping, and mRNA expression.

We have identified cDNAs clones for several cold-inducible mRNAs from the brown adipose tissue of mice. pCIN-1, a plasmid with a 900-base pair insert, encoded the mitochondrial uncoupling protein (UCP) as determined by the ability of the cDNA insert to select, by hybridization, an mRNA that could be translated into a 32,000-Da protein immunoprecipitable with anti-UCP antibodies. Nine tissues were analyzed; however, UCP cDNA hybridized to an mRNA species of 1.6 and 2.0 kilobase pairs only in brown adipose tissue. A maximum induction of 10-fold occurred within 6 h of exposure to cold (5 degrees C). A BamHI restriction fragment polymorphism detected by Southern blot analysis of genomic DNA in recombinant inbred mouse strains allowed us to map the UCP gene to Chromosome 8. The analysis of the UCP gene expression in diabetic (db) and obese (ob) mice maintained at 27 degrees C for 3 days followed by cold exposure for 4 h at 5 degrees C indicated that UCP mRNA levels in mutant mice were unaffected at 27 degrees C and only slightly reduced at 5 degrees C. Accordingly, the inability of diabetic and obese mice to thermoregulate is not associated with a lack of UCP mRNA induction.

Adipose Tissue, Brown↗
PubMed1982

Repair of alkylated DNA in Escherichia coli. Physical properties of O6-methylguanine-DNA methyltransferase.

An inducible methyltransferase of Escherichia coli acts on O6-methylguanine in DNA by conveying the methyl group to one of its own cysteine residues. The protein has now been purified to apparent homogeneity from a constitutively expressing strain. The homogeneous methyltransferase exhibits no DNA glycosylase or endonuclease activity on alkylated DNA. Further, the methyltransferase activity is strikingly resistant to heat inactivation under reducing conditions. The protein has Mr = 18,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, while the sedimentation coefficient and Stokes radius of the native enzyme yield Mr = 18,400. The amino acid composition of the purified protein shows 4 to 5 cysteine residues/transferase molecule. The methylated, inactive form of the transferase has an unaltered molecular weight.

Amino Acids↗
PubMedDate not supplied

Development of adrenergic and cholinergic cardiac control in larvae of the African clawed frog Xenopus laevis.

Cardiac responses (heart rate, stroke volume, and cardiac output) to cholinergic and adrenergic receptor stimulation were investigated in developing larvae of Xenopus laevis from Nieuwkoop and Faber (NF) stage 33/34 (newly hatched) to NF stage 53 (22 d after hatching). Effects on heart rate (fH), stroke volume (SV), and cardiac output (CO) were analyzed using in situ preparations and video-microscopic techniques to record the continually beating heart. The results show that administration of acetylcholine to the heart decreases heart rate as early as NF stage 40. A significant reduction in SV and CO following acetylcholine administration to the heart was found at NF stages 45-53. Epinephrine had no significant effect on fH, SV, or CO at any of the stages investigated. However, an adrenergic tonus on the heart is present already at NF stage 40 (11%). This tonus increases up to a maximum (44%) at NF stages 45-47, when the maximal heart rate is found during development of X. laevis. We conclude that acetylcholine has a negative chronotropic and possibly also inotropic effect on the heart very early in development of X. laevis. We also hypothesize that the high adrenergic tonus found at NF stages 45-47 is responsible, at least in part, for the peak in heart rate seen at these stages.

Acetylcholine↗