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Digitale Medien

Predominance of oxidative deamination in the metabolism of exogenous noradrenaline by the normal and chemically denervated human uterine artery (1992)

Branco, Domingas ; Caramona, Margarida ; Martel, Fatima ; [weitere]

Springer

Naunyn-Schmiedeberg's archives of pharmacology 346 (1992), S. 286-293

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ISSN: 1432-1912

Schlagwort(e): Human uterine artery ; Metabolism of noradrenaline ; Extraneuronal deamination ; MAO A and B ; Chemical denervation

Quelle: Springer Online Journal Archives 1860-2000

Thema: Medizin

Notizen: Summary Longitudinal strips were prepared from human uterine arteries obtained at hysterectomy. The artery had a low content of noradrenaline and dopamine, contrasting with a high content of the deaminated catechols, dihydroxyphenylglycol (DOPEG) and dihydroxymandelic acid (DOMA), which together represented 98% of endogenous catechols. When incubated with 3H-noradrenaline (0.1 μmol/l), the uterine artery removed, accumulated and metabolized noradrenaline. Deaminated metabolites predominated, DOMA being the most abundant metabolite. Cocaine markedly reduced the accumulation of 3H-noradrenaline and abolished 3H-DOPEG formation, but did not change 3H-DOMA. Selective monoamine oxidase (MAO) inhibitors (clorgyline, selegiline and 2-amino ethyl carboxamide derivatives) caused a marked decrease in the amounts of 3H-DOPEG, 3H-DOMA and 3H-O-methylated and deaminated metabolites (OMDA) formed by the tissue and an increase in 3H-normetanephrine (NMN) formation. Inhibition of catechol-O-methyltransferase suppressed NMN formation and reduced that of OMDA; hydrocortisone slightly depressed the formation of DOMA and OMDA. Homogenates of the uterine artery deaminated 3H-5-HT, 14C-phenylethylamine and 3H-tyramine; inhibition curves of the deamination of 3H-tyramine by clorgyline and selegiline were compatible with the presence of both MOA A and MOA B. Exposure of the strips to 6-hydroxydopamine (1.5 mmol/l for 20 min; 3 exposure periods followed by washout periods of 15,15 and 30 min) resulted in complete and selective chemical denervation of the arterial tissue. This chemical denervation had effects which were similar to those of cocaine. The 2-amino ethyl carboxamide derivatives markedly reduced the formation of deaminated metabolites by the denervated strips. The semicarbazide-sensitive amine oxidase inhibitor semicarbazide reduced the formation of 3H-DOMA and 3H-DOPEG in intact strips, but was devoid of action in the denervated ones. It is concluded that, in the human uterine artery, deamination predominates over O-methylation and that extraneuronal deamination, leading to the formation of DOMA (and of OMDA) plays a major role in the metabolism even of low concentrations of exogenous noradrenaline.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00173541

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Digitale Medien

Curious convergence with hypostatic hybrid equilibrium models (1997)

RAMSAY, A. C. A. ; MOITINHO DE ALMEIDA, J. P. B. ; MAUNDER, E. A. W.

Chichester : Wiley-Blackwell

Communications in Numerical Methods in Engineering 13 (1997), S. 541-552

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ISSN: 1069-8299

Schlagwort(e): hybrid-equilibrium finite elements ; statically admissible stress fields ; spurious kinematic modes ; self-stressing modes ; Engineering ; Numerical Methods and Modeling

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik , Technik allgemein

Notizen: The paper describes an unexpected type of convergence behaviour occurring for a single, variable degree, primitive-type equilibrium element. For this element the number of independent stress fields is less than the number of independent boundary displacement variables that do not correspond to rigid element modes of displacement. This leads to the conclusion that the element is hypostatic and that, in the absence of self-stressing modes, no convergence can occur. Such ‘conventional’ counting procedures do not, however, reveal the whole picture, and numerical determination of the rank of the coefficient matrix of the equilibrium equations shows that, in practice, self-stressing modes can and do exist in a model which would conventionally be described as hypostatic. The rank deficiency in the coefficient matrix is shown to be due to the fact that, upon transformation, independent stress fields do not necessarily lead to independent boundary tractions. Generalization to conventionally iso- and hyperstatic models demonstrates that, whenever the coefficient matrix is rank-deficient, spurious kinematic modes coexist with self-stressing modes. The problem which reveals the curious convergence characteristics for the primitive-type element is resolved using a macro-type element, and it is seen that, with the larger degree of hyperstaticity available to this element, strictly monotonic convergence characteristics are observed. © 1997 John Wiley & Sons, Ltd.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

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Digitale Medien

A GENERAL FORMULATION OF EQUILIBRIUM MACRO-ELEMENTS WITH CONTROL OF SPURIOUS KINEMATIC MODES: THE EXORCISM OF AN OLD CURSE (1996)

MAUNDER, E. A. W. ; DE ALMEIDA, J. P. MOITINHO ; RAMSAY, A. C. A.

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 39 (1996), S. 3175-3194

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ISSN: 0029-5981

Schlagwort(e): equilibrium elements ; spurious kinematic modes ; macro-elements ; Engineering ; Engineering General

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik , Technik allgemein

Notizen: This paper illustrates a method whereby a family of robust equilibrium elements can be formulated in a general manner. The effects of spurious kinematic modes, present to some extent in all primitive equilibrium elements, are eliminated by judicious assembly into macro-equilibrium elements. These macroelements are formulated with sufficient generality so as to retain the polynomial degree of the stress field as a variable. Such a family of macro-elements is a new development, and results for polynomials of degree greater than two have not been seen before. The quality of results for macro-equilibrium elements with varying degrees of polynomial is demonstrated by numerical examples.

Zusätzliches Material: 14 Ill.

Materialart: Digitale Medien

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