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- Burgess, G.M., et al.
(författare)
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Further studies on the interactions between the calcium mobilization and cyclic AMP pathways in guinea pig hepatocytes
- 1986
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Ingår i: Molecular Pharmacology. - : American Society for Pharmacology and Experimental Therapeutics. - 0026-895X .- 1521-0111. ; 30:4, s. 315-320
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Tidskriftsartikel (refereegranskat)abstract
- Isoproterenol (50 nM) potentiated the effects of angiotensin (1-50 nM) on 86Rb efflux and 45Ca efflux from guinea pig hepatocytes. This effect occurred in the presence or absence of extracellular Ca2+ and required the simultaneous presence of both isoproterenol and angiotensin. Neither the divalent cationophore, A23187, nor 4 beta-phorbol dibutyrate could substitute for angiotensin. The effects of isoproterenol were greatest with submaximal concentrations of angiotensin, whereas maximal concentrations of angiotensin were affected little. Isoproterenol did not substantially increase the formation of [3H]inositol triphosphate or the ratio of isomers [3H]inositol 1,4,5-trisphosphate and [3H]inositol 1,3,4-trisphosphate formed in response to angiotensin. Isoproterenol also enhanced the phase of Ca2+ mobilization involving Ca2+ entry which is consistent with the previously proposed functional linkage between receptor-regulated Ca2+ release and Ca2+ entry. These findings suggest that isoproterenol may act by increasing the sensitivity of the endoplasmic reticulum to the Ca2+-releasing action of inositol 1,4,5-trisphosphate.
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- Connolly, Eamonn, et al.
(författare)
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Norepinephrine-induced Na+ influx in brown adipocytes is cyclic AMP-mediated
- 1986
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 261:31, s. 14377-14385
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Tidskriftsartikel (refereegranskat)abstract
- To examine the involvement of Na+ ions in adrenergic responses in brown adipose tissue, a method is described for measuring Na+ influx into isolated brown adipocytes, using short (30 s) incubations with 22Na+, followed by a two-step centrifugation recovery procedure. Using this method, a clear norepinephrine-stimulated accumulation of intracellular 22Na+ was observed, which was enhanced by the addition of ouabain, was insensitive to amiloride (a Na+/H+ exchange blocker), and could not be mimicked by the total removal of oxygen from the incubation medium. The norepinephrine-stimulated Na+ influx was dose-dependent for the hormone with an EC50 of 250 nM, was blocked by the beta-antagonist propranolol but not by the alpha 1-antagonist prazosin, and could be induced by adrenergic agonists with the order of potency: isoproterenol greater than norepinephrine greater than phenylephrine, indicating a beta-receptor-mediated process. The Na+ influx was found to be cAMP-dependent since it could be induced by both theophylline (a phosphodiesterase inhibitor) and forskolin (an adenylate cyclase activator), but it was independent of other known cellular cAMP-dependent responses since neither addition of fatty acid substrates (octanoate or palmitate), nor of the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone could induce the phenomenon, despite having significant stimulatory effects on cellular respiration. Furthermore, total respiratory inhibition with rotenone, or total oxygen depletion of the medium with dithionite, did not prevent the normal norepinephrine-induced Na+ influx. The possibility that this beta-mediated norepinephrine-stimulated Na+ influx plays an important physiological role in brown adipose tissue activity is discussed, perhaps as one of the, as yet undefined, signals initiating tissue growth in the chronically beta-stimulated tissue of animals facing long-term increases in thermogenic demands.
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- Hansson, Pär, 1957-
(författare)
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Intra-industry trade: measurements, determinants and growth : a study of Swedish foreign trade
- 1989
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The conclusions are that a traditional factor proportions model seems neither theoretically nor empirically to explaing IIT. However, a relaxation of the assumption of homogeneous products in an industry gives rise to several implications for IIT. Industry characteristics such as an industry’s factor intensity and the degree of product differentiation play important roles. The more extreme an industry is with regard to factor intensity, i.e., if an industry is very capital or very labor intensive, the smaller IIT is in that industry. The more differentiated the products, the less the elasticity of substitution in demand between different products in an industry, the larger the IIT. In order to test the latter, a new measure of product differentiation closely related to the concept in the theoretical model is developed. Furthermore, similarity in relative factor endowments in the trading countries and transaction costs - tariffs and transport costs - influence IIT. The more similar the relative factor endowments, the larger the IIT. The less the transaction costs, the greater the IIT.
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- Hydén, Dag, et al.
(författare)
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Visual suppression tests in acoustic neuroma patients
- 1989
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Ingår i: Acta oto-laryngologica. Supplementum. - : Informa UK Limited. - 0365-5237 .- 1651-2464 .- 0001-6489 .- 1651-2251. ; 108:s468, s. 349-351
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Tidskriftsartikel (refereegranskat)abstract
- Fifty-five patients with a unilateral acoustic neuroma were investigated preoperatively with visual suppression tests during rotatory oscillation and caloric irrigation. During a sinusoidal oscillation, 29% of the patients showed a reduced suppression compared to 9% during pseudo-random oscillation and 11 % in the caloric test. In the sinusoidal and caloric tests the majority of the patients with deficient suppression had large or medium-sized tumors. In a few patients with small tumors, pathology was observed in both sinusoidal and randomized tests, presumably as a sign of unconcentration. The study shows that the sinusoidal visual suppression test and to a lesser degree suppression during caloric irrigation are of value for identification of brainstem-cerebellum compression of acoustic neuromas.
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