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Infection and Inflammation
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Erik H. J. G. Aarntzen, Andor W. J. M. Glaudemans
Lipophilic agents like oxine, hexamethyl-propylene amine oxime (HMPAO), pyruvaldehyde-bis-N4-methylthiosemicarbazone (PTSM), and tropolone passively diffuse over the cell membrane, complexes fall apart in the cytoplasma by reduction, and the radionuclide dissociates and binds to intracellular proteins. Of these, oxine and HMPAO are mostly used for labelling general leukocyte populations in infection and inflammation [29–31].
Sympathetic Neurotransmission
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
One of the first COMT inhibitors to be described was pyrogallol. Many of the inhibitors of COMT are either catechols or, like pyrogallol, have three hydroxyl substituents on the benzene ring (Figure 2.18). Pyrogallol and catechol derivatives serve as competitive substrates for COMT and inhibit the enzyme both in vitro and in vivo. This author showed the COMT inhibitory properties of catechol, pyrogallol and two acid degradation products of noradrenaline, noradnamine and diadrenaline ether (Abbs et al. 1967). Pyrogallol, however, has a high toxicity in vivo attributed to inhibition of other enzyme systems and to the formation of methaemoglobin (Guldberg & Marsden 1975) and thus has no clinical use. Subsequently, tropolone and U-0521 (3,4-dihydroxy-2-methylpropiophenone) have been shown to have COMT inhibitory properties. Tropolone appears to inhibit by formation of an enzyme-Mg2+-tropolone complex; it is toxic and like U-0521 is ineffective after oral administration and therefore of no clinical use. U-0521, however, is a widely used tool drug for examining the role of COMT. Newer orally active and potent
A fast, miniaturised in-vitro assay developed for quantification of lipase enzyme activity
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Ariane Menden, Davane Hall, Daniel Paris, Venkatarian Mathura, Fiona Crawford, Michael Mullan, Stefan Crynen, Ghania Ait-Ghezala
Moreover, the assay was used to verify the impact of the new in-silico determined allosteric modulator Tropolone on CRL activity. Tropolone is a seven-carbon aromatic ring, which is a common motif in naturally occurring compounds. It was shown to inhibit the grape polyphenol oxidase as well as the mushroom tyrosinase29,30. So far, it has not been reported that Tropolone can inhibit lipases, although other natural compound classes such as flavonoids, alkaloids, and saponins are known to inhibit CRL’s activity with varying efficacy depending on the used concentration25,26.