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| 2. |
- Persson, Bengt L., et al.
(författare)
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ATP-driven transhydrogenase provides an example of delocalized chemiosmotic coupling in reconstituted vesicles and in submitochondrial particles
- 1987
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 894:2, s. 239-251
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of coupling between mitochondrial ATPase (EC 3.6.1.3) and nicotinamide nucleotide transhydrogenase (EC 1.6.1.1) was studied in reconstituted liposomes containing both purified enzymes and compared with their behavior in submitochondrial particles. In order to investigate the mode of coupling between the transhydrogenase and the ATPase by the double-inhibitor and inhibitor-uncoupler methods, suitable inhibitors of transhydrogenase and ATPase were selected. Phenylarsine oxide and A3′-O-(3-(N-(4-azido-2-nitrophenyl)amino)propionyl)-NAD+ were used as transhydrogenase inhibitors, whereas of the various ATPase inhibitors tested aurovertin was found to be the most convenient. The inhibition of the ATP-driven transhydrogenase activity was proportional to the inhibition of both the ATPase and the transhydrogenase. Inhibitor-uncoupler titrations showed an increased sensitivity of the coupled reaction towards carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) — an uncoupler that preferentially uncouples localized interactions, according to Herweijer et al. (Biochim. Biophys. Acta 849 (1986) 276–287) — when the primary pump was partially inhibited. However, when the secondary pump was partially inhibited the sensitivity towards FCCP remained unchanged. Similar results were obtained with submitochondrial particles. These results are in contrast to those obtained previously with the ATP-driven reverse electron flow. In addition, the amount of uncoupler required for uncoupling of the ATP-driven transhydrogenase was found to be similar to that required for the stimulation of the ATPase activity, both in reconstituted vesicles and in submitochondrial particles. Uncoupling of reversed electron flow to NAD+ required much less uncoupler. On the basis of these results, it is proposed that, in agreement with the chemiosmotic model, the interaction between ATPase and transhydrogenase in reconstituted vesicles as well as in submitochondrial particles occurs through the [...]. In contrast, the energy transfer between ATPase and NADH-ubiquinone oxidoreductase appears to occur via a more direct interaction, according to the above-mentioned results by Herweijer et al.
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| 3. |
- Persson, Bengt L., et al.
(författare)
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NBD-Cl modification of essential residues in mitochondrial nicotinamide nucleotide transhydrogenase from beef heart
- 1988
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Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology. - : Elsevier BV. - 0167-4838 .- 1879-2588. ; 953, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- Modification of mitochondrial nicotinamide nucleotide transhydrogenase (NADPH:NAD+ oxidoreductase, EC 1.6.1.1) with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), followed by measurement of the absorption or fluorescence of the transhydrogenase-NBD adducts, resulted in a biphasic labelling of approx. 4–6 sulfhydryls, presumably cysteine residues. Of these 1–2 (27%) were fast-reacting and 3–4 (73%) slow-reacting sulfhydryls. In the presence of substrates, e.g., NADPH, the labelling was monophasic and all sulfhydryls were fast-reacting, suggesting that the modified sulfhydryls are predominantly localized peripheral to the NAD(P)(H)-binding sites. The rates of modification allowed the calculation of the rate constants for each phase of the labelling. Both in the absence and in the presence of a substrate, e.g., NADPH, the extent of labelling essentially parallelled the inhibition of transhydrogenase activity. Attempts to reactivate transhydrogenase by reduction of labelled sulfhydryls were not successful. Photo-induced transfer of the NBD adduct in partially inhibited transhydrogenase, from the sulfhydryls to reactive NH2 groups of amino-acid residue(s), identified as lysine residue(s), was parallelled by an inhibition of the residual transhydrogenase activity. It is suggested that a lysine localized close to the fast-reacting NBD-Cl-reactive sulfhydryl groups is essential for activity.
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| 5. |
- Carlenor, E, et al.
(författare)
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On the presence of a nicotinamide nucleotide transhydrogenase in mitochondria from potato tuber
- 1988
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 88, s. 303-308
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria isolated from potato (Solanum tuberosum L.) tuber wereinvestigated for the presence of a nicotinamide nucleotide transhydrogenaseactivity. Submitochondrial particles derived from these mitochondriaby sonication catalyzed a reduction of NAD' or 3-acetylpyridine-NAD'by NADPH, which showed a maximum of about 50 to 150 nanomoles/minute. milligram protein at pH 5 to 6. The Km values for 3-acetylpyridine-NAD' and NADPH were about 24 and 55 micromolar, respectively.Intact mitochondria showed a negligible activity in the absence of detergents.However, in the presence of detergents the specific activity approachedabout 30% of that seen with submitochondrial particles. Thepotato mitochondria transhydrogenase activity was sensitive to trypsinand phenylarsine oxide, both agents that are known to inhibit the mammaliantranshydrogenase. Antibodies raised against rat liver transhydrogenasecrossreacted with two peptides in potato tuber mitochondrialmembranes with a molecular mass of 100 to 115 kilodaltons. Theobserved transhydrogenase activities may be due to an unspecific activityof dehydrogenases and/or to a genuine transhydrogenase. The activitycontributions by NADH dehydrogenases and transhydrogenase to thetotal transhydrogenase activity were investigated by determining theirrelative sensitivities to trypsin. It is concluded that, at high or neutralpH, the observed transhydrogenase activity in potato tuber submitochondrialparticles is due to the presence of a genuine and specific highmolecular weight transhydrogenase. At low pH an unspecific reaction ofan NADH dehydrogenase with NADPH contributes to the total transhydrogenaseactivity.
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| 8. |
- Ernfors, P, et al.
(författare)
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Developmental and regional expression of beta-nerve growth factor receptor mRNA in the chick and rat.
- 1988
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Ingår i: Neuron. - 0896-6273 .- 1097-4199. ; 1:10, s. 983-96
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Tidskriftsartikel (refereegranskat)abstract
- Hybridization probes from the transmembrane region of the chick NGF receptor (NGF-R) that show high homology with the rat NGF-R were used to demonstrate an abundant 4.5 kb NGF-R mRNA in the chick embryo at E3.5. The level remained high until E12 but decreased to adult levels by E18. The highest levels at E8 were in spinal cord, bursa of Fabricius, gizzard, femoralis muscle, and skin. In situ hybridization to E7 embryos showed high expression of the NGF-R gene in spinal cord, particularly the lateral motor column, and in dorsal root, sympathetic, and nodose ganglia. NGF-R mRNA expression was observed throughout brain development and in all regions of the adult brain, with high levels in cerebellum and septum. Lymphoid tissues of chick and rat also expressed the receptor. The complex and widespread expression of NGF-R mRNA in areas not known to be NGF targets suggests broader functions for NGF.
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| 9. |
- Eytan, G D, et al.
(författare)
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Energy-linked nicotinamide-nucleotide transhydrogenase. Characterization of reconstituted ATP-driven transhydrogenase from beef heart mitochondria.
- 1987
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 262, s. 5008-5014
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between pure transhydrogenase and ATPase (Complex V) from beef heart mitochondria was investigated with transhydrogenase-ATPase vesicles in which the two proteins were co-reconstituted by dialysis or dilution procedures. In addition to phosphatidylcholine and phosphatidylethanolamine, reconstitution required phosphatidylserine and lysophosphatidylcholine. Transhydrogenase-ATPase vesicles catalyzed a 20-30-fold stimulation of the reduction of NADP+ or thio-NADP+ by NADH and a 70-fold shift of the apparent equilibrium expressed as the nicotinamide nucleotide ratio [NADPH][NAD+]/[NADP+][NADH]. In both of these respects, the transhydrogenase-ATPase vesicles were severalfold more efficient than beef heart submitochondrial particles. By measuring the ATP-driven transhydrogenase and the oligomycin-sensitive ATPase activities simultaneously and under the same conditions at low ATP concentrations, i.e. below 15 microM, the ATP-driven transhydrogenase/oligomycin-sensitive ATPase activity ratio was found to be about 3. This value is consistent with the stoichiometries of three protons translocated per ATP hydrolyzed and one proton translocated per NADPH formed and with a mechanism where the two enzymes interact through a delocalized proton-motive force.
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| 10. |
- Henriksen, O., et al.
(författare)
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In vivo evaluation of femoral blood flow measured with magnetic resonance
- 1989
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 30:2, s. 153-157
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative measurements of blood flow based on magnetic resonance imaging (MRI) using conventional multiple spin echo sequences were evalutated in vivo in healthy young volunteers. Blood flow was measured using MRI in the femoral vein. The initial slope of the multiple spin echo decay curve, corrected for the T2 decay of non-flowing blood was used to calculate the blood flow. As a reference, the blood flow in the femoral artery was measured simultaneously with an invasive indicator dilution technique. T2 of non-flowing blood was measured in vivo in popliteal veins during regional circulatory arrest. The mean T2 of non-flowing blood was found to be 105 ±31 ms. The femoral blood flow ranged between 0 and 643 ml/min measured with MRI and between 280 and 531 ml/min measured by the indicator dilution technique. There was thus poor agreement between the two methods. The results indicate that in vivo blood flow measurements made with MRI based on wash-out effects, commonly used in multiple spin echo imaging, do not give reliable absolute values for blood flow in the femoral artery or vein.
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| 11. |
- Kotlikoff, Laurence J., et al.
(författare)
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Social Contracts as Assets : A Possible Solution to the Time-Consistency Problem
- 1987
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a new solution to the time-consistency problem that appears capable of enforcing ex ante policy in a variety of settings in which other enforcement mechanisms do not work. The solution involves formulating a social contract, institution, or agreement that specifies the optimal ex ante policy. The social contract is effectively sold by succesive old generations to successive young generations, who pay for the social contract through the payment of taxes. Both old and young generations have an economic incentive to fulfill the social contract. For the old generation, breaking the social contract makes the social contract valueless, and the generation suffers a capital loss by not being able to sell it. For the young generation the economic advantage of purchasing the existing social contract exceeds its price as well as the economic gain from setting up the a new social contract.
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| 12. |
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| 13. |
- Persson, Bengt L., et al.
(författare)
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Energy-linked nicotinamide nucleotide transhydrogenase. Hydrodynamic properties and active form of purified and membrane-bound mitochondrial transhydrogenase from beef heart
- 1987
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861 .- 1096-0384. ; 259:2, s. 341-349
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial nicotinamide nucleotide transhydrogenase from beef heart was investigated with respect to minimal assembly of the purified enzyme and of the enzyme in the mitochondrial inner membrane. Studies of the hydrodynamic properties of the purified enzyme in the presence of 0.3% Triton X-100 allowed determination of the Stokes radius, sedimentation constant, partial specific volume, frictional ratio, and molecular weight. Under these conditions transhydrogenase existed as an inactive monomer, suggesting that monomerization may be accompanied by inactivation. Radiation inactivation was used to determine the functional molecular size of purified detergent-dispersed transhydrogenase and transhydrogenase in beef heart submitochondrial particles. Under these conditions the catalytic activity of both the purified and the membrane-bound enzyme was found to be catalyzed by a dimeric form of the enzyme. These results suggest for the first time that the minimal functional assembly of detergent-dispersed as well as membrane-bound transhydrogenase is a dimer, which is not functionally associated with, for example, complex I or ATPase. In addition, the results are consistent with the possibility that the two subunits of transhydrogenase are catalytically active in an alternating fashion according to a previously proposed half-of-the-sites reactivity model.
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| 14. |
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| 15. |
- Persson, E, et al.
(författare)
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Plasma lipolytic activity after subcutaneous administration of heparin and a low molecular weight heparin fragment
- 1987
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Ingår i: Thrombosis Research. - : Elsevier BV. - 1879-2472 .- 0049-3848. ; 46:5, s. 697-704
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Tidskriftsartikel (refereegranskat)abstract
- The effect of heparin and a low molecular weight heparin fragment (LMWH, mean molecular weight 4000-6000) on plasma anticoagulation and lipolysis was studied in eight healthy men. The activities of antifactor Xa (antiFXa), lipoprotein lipase (LPL), hepatic lipase (HL) and plasma levels of free fatty acids (FFA) were analysed after the injection of 5000 antiFXa units of heparin or LMWH subcutaneously. In comparison with heparin, the administration of LMWH resulted in a significantly higher antiFXa activity (p less than 0.001) but a lower release of LPL and HL (p less than 0.001), which did not increase plasma FFA. It is concluded that subcutaneous injection of LMWH in men elicits an adequate anticoagulant effect measured as antiFXa activity but has a negligible effect on plasma lipolytic activity.
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| 16. |
- Persson, W, et al.
(författare)
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Spectrum of Doubly Ionized Xenon (xe-iii)
- 1988
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Ingår i: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 38:3, s. 347-369
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Tidskriftsartikel (refereegranskat)
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