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Biomedical subjects

O C Ingebretsen

Publications and source records attributed to O C Ingebretsen.

35 records · Page 2Linked to original sources
PubMed1980

Direct measurement of free coenzyme A in biological extracts by reversed-phase high-performance liquid chromatography.

A high-performance liquid chromatographic system was developed with baseline separation of coenzyme A (CoASH) from dephospho-coenzyme A and acetyl-coenzyme A using isocratic elution. The chromatographic separation was achieved in a reversed-phase system with a high concentration (220 mM) of potassium phosphate buffer at pH 4.0 and appropriate amounts of methanol (ca. 12%). The eluate was monitored with a UV detector at 254 nm with the limit of detection at ca. 5 pmoles. The system could be used without modification for the estimation of the content of CoASH in biological extracts, e.g. mitochondria.

Animals↗
PubMed1980

Subcellular distribution of ascorbate in bovine adrenal medulla. Evidence for accumulation in chromaffin granules against a concentration gradient.

The subcellular distribution of ascorbate and catecholamines has been studied in homogenates of bovine adrenal medulla and cortex. 1. The recovery of the vitamin was found to be 4.10 +/- 0.22 and 9.57 +/- 1.37 mumol/g wet weight for the medulla and cortex, respectively. A major fraction (34.4%) of the vitamin was recovered in the particulate fraction of the medulla as compared to about 8% in the corresponding fraction of the cortex. In comparison, 78.9% of the catecholamines were found in the particulate fraction of the medulla. 2. Analytical differential centrifugation of medulla homogenates revealed a sedimentation profile of ascorbate which was identical to that obtained for noradrenalin and adrenalin. The co-sedimentation of these compounds indicates that ascorbate is an essential component of the heavy as well as the light population of chromaffin granules. The stoichiometry of catecholamines to ascorbate was approx. 25:1 in both subpopulations. 3. Based on an estimated volume fraction of approximately 13% for the chromaffin granules, as determined morphometrically (Kryvi, H., Flatmark, T. and Terland, O. (1979) Eur. J. Cell Biol. 20, 76-82), a concentration gradient (chromaffin granules:cytosol) of approx. 4 was estimated for ascorbate in the cells of adrenal medulla. 4. No ascorbate 2-sulfate was detected in any of the subcellular fractions isolated, and the content of dehydroascorbate in isolated chromaffin granules was less than 1% of the total ascorbate value.

Adrenal Cortex↗
PubMed1978

Fluorimetric detection of octopamine in high-performance liquid chromatography and its application to the assay of dopamine beta-monooxygenase in human serum.

A high-performance liquid chromatographic procedure is described for the determination of octopamine. The method, which is based on the separation on a microparticulate bonded strong cation-exchange resin and measurement of the native fluorescence, has been applied to give a sensitive assay of dopamine beta-monooxygenase (EC 1.14.17.1) activity in human serum with tyramine as the substrate. The procedure, which has been designed for use with an automatic sampler, has a detection limit of about 50 pmoles of octopamine, and the analysis time is approximately 10 min per sample.

Autoanalysis↗
PubMed1978

On the rate-limiting step in the transfer of long-chain acyl groups across the inner membrane of brown adipose tissue mitochondria.

Brown adipose tissue mitochondria predominantly oxidize fatty acids in order to generate heat for non-shivering thermogenesis, and have an unusually high capacity for net transfer of long-chain fatty acyl groups from the outer to the inner (matrix) compartment. The activities of the "outer" and "inner" carnitine long-chain acyltransferases have been estimated in isolated mitochondria of cold-acclimated guinea pits by the continuous spectrophotometric recording of the redox level of flavoproteins in the acyl-CoA dehydrogenase pathway. This redox level is determined by the intramitochondrial content of acyl-CoA under the selected experimental conditions. The apparent initial rate of the "inner" acyltransferase (palmitoyl-L-carnitine added) is three order of magnitudes higher than the "outer" acyltransferase (palmitoyl-CoA added), and this difference is not influenced by the substrate concentration, pH and reaction temperature. Thus, the "outer" acyltransferase reaction is rate limiting in the transfer of long-chain acyl groups across the inner membrane of these mitochondria and catalyzes a non-equilibrium reaction in the intact organelle. Estimates of the absolute rate of the "outer" long-chain acyltransferase indicate that it exceeds that of rat liver mitochondria by a factor of 20.

Acclimatization↗
PubMed1976

Mechanism of the inhibitory effect of glyoxylate plus oxaloacetate and oxalomalate on the NADP-specific isocitrate dehydrogenase.

The effects of glyoxylate plus oxaloacetate and of oxalomalate on the NADP-linked isocitrate dehydrogenase (threo-DS-isocitrate:NADP+ oxidoreductase (decarboxylating, EC 1.1.1.42) from pig heart from been studied with steady state methods as well as with stopped flow technique. When equimolar mixtures of glyoxylate and oxaloacetate were premixed for different lengths of time prior to addition to the assay mixture, the extent of inhibition increased with the premixing time. The results indicated that the inhibition by glyoxylate plus oxaloacetate is caused by a compound formed in a reversible interaction between the two components. Glyoxylate plus oxaloacetate and oxalomalate affected the enzyme in at least three different ways. They inhibited the enzyme in a reaction competitive with regard to the substrate isocitrate. This inhibition needed a certain time to be fully expressed. The time lag could be eliminated by premixing of the enzyme and inhibitor with NADP plus metal ion. Secondly, if the enzyme is premixed with NADP plus metal ions, a time lag occurs before the reaction rate approaches a constant value after initiation of the reaction with isocitrate. The inhibitors were found to enhance this effect of NADP plus metal ions on the enzyme. Thirdly, it has previously been shown that the enzyme can be activated by metal complexing agents. Glyoxylate plus oxaloacetate as well as oxalomalate are able to form complexes with metal ions and were found to cause an initial activation of the enzyme under certain assay conditions. The controversy regarding the mechanism of action of the above inhibitors on the enzyme is probably due to the fact that they affect the enzyme in several different ways.

Animals↗
PubMed1976

Variation in levels of enzymes related to energy metabolism in alternative developmental pathways of Blastocladiella emersonii.

The activities of phosphofructokinase (PFK), fructose diphosphatase (FDP), nicotinamide adenine dinucleotide (NAD) and NAD phosphate (NADP)-linked isocitrate dehydrogenases (IDHNAD, IDHNADP), two NAD-linked glutamate dehydrogenases (GDH1, GDH2), and isocitrate lyase were studied during the development of the two phenotypes, ordinary colorless and resistant sporangia (OC and RS plants), of water mold Blastocladiella emersonii in synchronized liquid cultures. The OC plants had a generation time of about 12 h, whereas the RS plants required 3.5 days to reach maturity. All the enzymes were present throughout the development of both phenotypes. In zoospores, PFK, FDP, and GDH2 were localized in the cytosol. The IDHNADP activity was distributed with two-thirds in the soluble and one-third in the particulate fraction. GDH1 and IDHNAD showed the same distribution and were predominantly present in the particulate fraction, presumably in the mitochondria. Isocitrate lyase was found in the particulate fraction. The enzyme levels changed considerably during development. FDP and IDHNADP varied in a parallel manner. Similarly, the three enzymes PFK, IDHNAD and GDH1 showed parallel variations. The activity patterns for all enzymes were different for the OC and RS pathways. Isocitrate lyase exhibited the largest changes in activity during development. Thus, during OC plant formation, its activity decreased by a factor of 20. GDH2 varied similarly to PFK and IDHNADP during OC plant development, whereas it behaved like isocitrate lyase during RS plant development. The ratios between anabolic and catabolic enzymes were higher in mature plants than in zoospores and higher in RS plants than in OC plants. The results indicate that the variations in the enzyme levels are secondary to the critical changes involved in the transition from one developmental pathway to the other.

Blastocladiella↗
PubMed1975

Properties of the nicotinamide adenine dinucleotide phosphate-specific isocitrate dehydrogenase from Blastocladiella emersonii.

The nicotinamide adenine dinucleotide phosphate (NADP)-specific isocitrate dehydrogenase from Blastocladiella emersonii was purified. The enzyme was very unstable. Satisfactory stability was obtained in the presence of 0.2% ovalbumin. The enzyme had a molecular weight of about 100,000. It did not exhibit homotropic cooperativity for any of it substrates and was not affected by the allosteric modifiers citrate and adenosine monophosphate, diphosphate, and tri-phosphate. The substrate saturation studies showed both intercept and slope effects in Lineweaver-Burk plots. The Km values for isocitrate and NADP were found to be 20 and 10 muM, respectively. The product inhibition pattern was compatible with a random sequential reaction mechanism. The enzyme catalyzed the oxidative decarboxylation of isocitrate about six times better than the reductive carboxylation of alpha-ketoglutarate. The enzyme was inhibited by glyoxylate plus oxalacetate. Assays conducted in the presence of low Mg2+ concentrations exhibited a lag. This lag could be abolished by the addition of reduced NADP to the assay mixture.

Blastocladiella↗
PubMedDate not supplied

Does VLDL-LDL-cholesterol in cord serum predict future level of lipoproteins?

Lipoproteins were measured in 618 healthy, full-term newborns. Seventy-four with a VLDL-LDL-cholesterol above 1.3 mmol/l (50 mg/dl) at birth and 25 randomly chosen controls with VLDL-LDL-cholesterol 1.3 mmol/l or below at birth were followed up at age 2. Seventy-two (52 in the high VLDL-LDL-cholesterol group and 20 in the low VLDL-LDL-cholesterol group) were followed up at age 13. At age 2 mean total cholesterol was 5.48 mmol/l (SEM 0.10) in the children with a high VLDL-LDL-cholesterol at birth, compared to 4.69 mmol/l (SEM 0.17) in the children with a low VLDL-LDL-cholesterol at birth (p less than 0.001). A difference was still present at age 13 (4.74 mmol/l; SEM 0.11 versus 4.20 mmol/l; SEM 0.14; p less than 0.01). At age 13 apolipoprotein B was 0.74 g/l (SEM 0.02) in the children with a high VLDL-LDL-cholesterol at birth, compared to 0.65 g/l (SEM 0.02) in the children with a low VLDL-LDL-cholesterol at birth (p less than 0.01). Children with high VLDL-LDL-cholesterol at birth might be more liable to high lipoprotein serum levels later in life.

Apolipoprotein A-I↗