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  • Rat heart  (2)
  • sympathetic tone  (2)
  • 81R50  (1)
  • Covariant deformations  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Deformations covariantes sur les orbites polarisees d'un groupe de Lie
    Amsterdam : Elsevier
    Journal of Geometry and Physics 14 (1994), S. 309-331 
    Details
    ISSN: 0393-0440
    Keywords: Covariant deformations ; Lie groups ; [Mathematical Subject Codes] 14 D 15 ; [Mathematical Subject Codes] 22 E 30 ; [Mathematical Subject Codes] 22 E 70 ; [Mathematical Subject Codes] 58 H 15 ; polarised orbits
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0393-0440(94)90039-6
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition by K+ of uptake2 of3H-(±)-isoprenaline in the perfused rat heart (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 334 (1986), S. 393-396 
    Details
    ISSN: 1432-1912
    Keywords: Isoprenaline ; Uptake2 ; Extracellular potassium ; Rat heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The kinetics of the inhibitory effect of extracellular K+ on uptake2 of3H-(±)-isoprenaline were determined in isolated hearts obtained from reserpine-pretreated rats; catechol-O-methyl transferase was inhibited. 1. Initial rates of uptake2 of a very low concentration of3H-(±)-isoprenaline (10 nmol/l) were determined in the presence of various extracellular concentrations of K+ (2.7 to 60 mmol/l). The inhibitory effect of K+ was concentration-dependent with an IC50 of about 20 mmol/l. — In these experiments KCl was added to the perfusion solution, and some hypertonicity resulted. In some experiments NaCl was added to a solution containing 5 mmol/l K+ to result in the same degree of hypertonicity as that obtained for 60 mmol/l K+; hypertonicity increased the initial rate of uptake2 of3H-(±)-isoprenaline. Thus, the inhibitory effect of K+ had been slightly underestimated. 2. In subsequent experiments the increase of the concentration of K+ in the perfusion fluid to 30 mmol/l was compensated for by a corresponding reduction of Na+. Initial rates of uptake2 of 10 nmol/l3H-(±)-isoprenaline were determined in the absence and presence of various concentrations of unlabelled (±)-isoprenaline. At 30 mmol/l K+ the IC50 (=K m for uptake2) did not significantly differ from that determined in an earlier study of 2.7 mmol/l K+ (Grohmann and Trendelenburg 1984). Finally, theV max for uptake2 of3H-(±)-isoprenaline was determined at either 2.7 or 30 mmol/l K+. At 30 mmol/l K+ theV max was only about 1/4 of that observed at 2.7 mmol/l K+. 3. Extracellular K+ inhibits uptake2 of3H-(±)-isoprenaline primarily by a reduction ofV max.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00569376
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of partial inhibition of monoamine oxidase on the steady-state rate of deamination of 3H-catecholamines in two metabolizing systems (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 333 (1986), S. 253-261 
    Details
    ISSN: 1432-1912
    Keywords: Neuronal deamination ; Extraneuronal deamination ; Rat vas deferens ; Rat heart ; Monoamine oxidase ; Pargyline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two different “deaminating systems” were compared (i.e., intact tissues in which an uptake process translocates the 3H-catecholamine from the extracellular space to the intracellular MAO): 1) the adrenergic nerve endings of the rat vas deferens exposed to 10 nmol/l 3H-(−)-noradrenaline, and 2) the extraneuronal deaminating system of the rat heart perfused with 50 nmol/l 3H-(−)-adrenaline. Vesicular uptake and COMT were inhibited. In both systems MAO was partially inhibited by pargyline, and the steady-state tissue content of the 3H-catecholamine was determined as well as the steady-state rate of deamination. 1. Rat vas deferens (preincubated with 10–40 nmol/l pargyline for 30 min). Inhibition of neuronal MAO caused not more than a moderate decrease of the steady-state rate of deamination of 3H-(−)-noradrenaline, but the steady-state tissue content was greatly increased. Determinations of the activity of MAO in homogenates of vasa deferentia showed that preincubation with 10 and 20 nmol/l pargyline inhibited the enzyme by 80 to 95%. 2. Rat heart (of animals pretreated with 1 to 30 mg/kg pargyline). Inhibition of extraneuronal MAO caused a steep decline of the steady-state rate of deamination of 3H-(−)-noradrenaline but only a small rise in the steady-state tissue content. 3. The decisive difference between the two deaminating systems lies in the fact that the ratio “k mao/k out” (where the two k-values characterize the activity of the unsaturated intracellular MAO and the ability of the 3H-catecholamine to leave the relevant cells, respectively) is much higher for the neuronal deaminating system exposed to 3H-(−)-noradrenaline than for the extraneuronal deaminating system exposed to 3H-(−)-adrenaline. Whenever this ratio is high, pronounced (but incomplete) inhibition of MAO results in a very pronounced increase in the intracellular steady-state 3H-amine concentration (during exposure of the tissue to a 3H-catecholamine); as far as the steady-state rate of deamination is concerned, the pronounced rise in substrate concentration largely masks the pronounced degree of inhibition of MAO. When, however, the ratio is close to unity, inhibition of MAO fails to result in any pronounced increase in the intracellular steady-state 3H-amine concentration; as a consequence, any pronoumced inhibition of MAO is then reflected by a pronounced decrease of the steady-state rate of deamination. 4. From the present results it is concluded that, in experiments with intact tissues, the degree of inhibition of MAO cannot be derived from measurements of rates of deamination of 3H-catecholamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00512938
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  • 4
    Electronic Resource
    Electronic Resource
    Lie groups whose coadjoint orbits are of dimension smaller or equal to two (1995)
    Springer
    Letters in mathematical physics 33 (1995), S. 183-186 
    Details
    ISSN: 1573-0530
    Keywords: 16W30 ; 17Bxx ; 17B05 ; 81R50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We give a complete classification of the class of connected, simply connected Lie groups whose coadjoint orbits are of dimension smaller or equal to two.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00739806
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  • 5
    Electronic Resource
    Electronic Resource
    Plasma concentrations of noradrenaline and 3,4-dihydroxyphenylethyleneglycol under conditions of enhanced sympathetic activity (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 261-267 
    Details
    ISSN: 1432-1041
    Keywords: noradrenaline ; desipramine ; plasma DOPEG ; sympathetic tone ; orthostatic stress ; bicycle exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Antecubital venous blood was sampled at rest and during orthostasis or supine bicycle exercise. The plasma was analyzed for noradrenaline and 3,4-dihydroxyphenylethyleneglycol (DOPEG) by HPLC. Orthostasis resulted in increases in plasma concentrations of both noradrenaline and DOPEG. The magnitude of changes in both was dependent on the degree of orthostasis. In conditions of supine rest, sitting, and standing the plot of the geometric mean values of plasma DOPEG (ordinate) against those of plasma noradrenaline was linear, had a slope of about unity, and intersected the ordinate at a finite value of plasma DOPEG. After administration of desipramine (to block uptake1), plasma concentrations of DOPEG fell both at rest and during orthostasis. Moreover, desipramine abolished the plasma DOPEG response to orthostasis without affecting the plasma noradrenaline response. Hence, changes in plasma DOPEG brought about by changes in sympathetic tone are presynaptic in origin. The plasma concentration of DOPEG observed in the presence of desipramine was virtually identical with the ordinate intercept of the regression line relating plasma DOPEG to plasma noradrenaline in the absence of desipramine. This pool of plasma DOPEG (which amounted to about 75% of that observed at supine rest in the absence of desipramine) probably stems from intraneuronal noradrenaline leaking out of the storage vesicles of peripheral sympathetic neurones and may in part also be derived from the central nervous system. Supine bicycle exercise failed to increase plasma DOPEG. This may be due to the separation of the sampling site from the site of noradrenaline release (i.e. the exercising limbs) by organs involved in DOPEG extraction. The failure of plasma DOPEG to rise under these conditions may also be a consequence of increased blood flow in the exercising limbs, resulting in a marked decrease in the proportion of the released noradrenaline being recaptured by the sympathetic nerve endings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558263
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  • 6
    Electronic Resource
    Electronic Resource
    Haemodynamics as a determinant of the pharmacokinetics of and the plasma catecholamine responses to isoprenaline (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 493-500 
    Details
    ISSN: 1432-1041
    Keywords: isoprenaline ; desipramine ; total body fractional extraction ; cardiac output ; plasma catecholamines ; neuronal uptake ; sympathetic tone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The total body clearance and fractional extraction of isoprenaline (ISO) have been determined, and the relation between these parameters and cardiac output established. Whether desipramine, an inhibitor of neuronal uptake, altered the plasma catecholamine response to ISO was also investigated. Seven healthy subjects were given i.v., infusions of ISO in two, consecutive 25-min periods, at constant dose rates of 31–43 and 80–124 pmol·kg−1·min−1, respectively. The total-body (ER), pulmonary (ERp) and forearm (ERf) fractional extractions and the total body clearance (CL) of ISO were obtained from measurements of cardiac output and the steady-state ISO concentration in mixed central venous, arterial and forearm venous plasma. ISO-induced increases in cardiac output resulted in increases in CL, decreases in ER and no consistent change in ERf. ERp did not differ from zero. ISO also produced a dose-dependent increase in the mixed venous plasma concentrations of noradrenaline and 3,4-dihydroxyphenylglycol (DOPEG), and a decrease in that of adrenaline. Pretreatment with desipramine did not alter any of the pharmacokinetic parameters of ISO. Desipramine, however, reduced the mixed venous baseline plasma levels of noradrenaline (47%) and DOPEG (40%), and tended to reduce that of adrenaline (34%). It enhanced the plasma noradrenaline response 2.4-fold, abolished the plasma DOPEG response and did not alter the plasma adrenaline response to ISO. Hence, owing to its haemodynamic effects, ISO modifies its own pharmacokinetics which involve non-neuronal removal processes only. The increased DOPEG in plasma resulting from the ISO-induced increase in noradrenaline release was presynaptic in origin. Desipramine appears to reduce sympathetic activity. The enhancement by desipramine of the ISO-induced increase in plasma noradrenaline points towards recapture by neuronal uptake of at least 58% of the noradrenaline released in response to ISO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558130
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