published_or_final_version / Chinese Medicine / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available online.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

No description available.

<p dir="ltr">Mycobacterium abscessus (Mab) is a type of mycobacterium that is known for its remarkable resistance to a variety of antibiotics. This pathogen poses a significant risk for individuals with weakened immune systems as it can cause skin and soft tissue infections, pulmonary disease and disseminated infections. Mab's ability to expel antibiotics through efflux pumps and form strong biofilms makes it even more challenging to treat infections. Lipids form a major part of the extracellular matrix of Mab biofilms. Efflux pumps have been shown to export lipids to the cell surface. Despite ongoing research into Mab's antibiotic tolerance, there is still much to learn about the impact of efflux pump inhibitors (EPIs) on antibiotic resistance and lipid biosynthesis during biofilm development in Mab. In this study, we investigated the impact of the EPIs; CCCP (carbonyl cyanide m-chlorophenyl hydrazone), piperine (PIP), reserpine (RES), berberine (BER), and verapamil (VER) on efflux activity, biofilm formation, antibiotic resistance, and lipid biosynthesis in Mab during planktonic and biofilm growth conditions. We found that Mab cells had a higher tolerance to EPIs in biofilm-stimulating medium and that the presence of EPIs led to a decrease in minimum inhibitory concentrations of frontline antibiotics, reduced efflux activity within Mab cells, and significantly inhibited biofilm formation. We examined the effects of EPIs that inhibited biofilm formation on lipid metabolism in Mab using radiolabeling with 14C?palmitic acid and 14C-acetic acid which are precursors of lipid biosynthesis. We observed that the EPI berberine inhibited the incorporation of 14C-palmitic acid into glycopeptidolipids in the surface lipids of planktonic cells and increased cellular glycopeptidolipid (GPL) in biofilm cells. Verapamil-treated cells showed a 55 % increase in cellular trehalose monomycolate (TMM) compared to controls. Piperine-treated cells exhibited a 50 % increase in cardiolipin. The incorporation of 14C-acetate into biofilm cells showed that piperine-treated biofilm cells showed a 146 % increase in surface glycopeptidolipids. Overall, our study enhances our understanding of lipid biosynthesis in Mab, the effects of EPIs on Mab biofilms, efflux mechanisms, and antibiotic resistance and offers insights for combating Mab-related infections.</p>

published_or_final_version / abstract / Chinese Medicine / Master / Master of Philosophy

Depuis les cinquante dernières années, l'incidence de la maladie de Crohn,maladie chronique inflammatoire de l'intestin (MICI) a plus que doublée. C'est une pathologie multifactorielle et idiopathique utilisant des traitements comme des anti-inflammatoires, des corticoïdes, des immunosuppresseurs et plus récemment les anti-TNF.Ils présentent des limites avec une intolérance aux principes actifs et une résistance au traitement conduisant à un échec thérapeutique. L’objectif de ce travail sera de développer une forme orale tout en minimisant le risque d’effets secondaires en améliorant la biodisponibilité. Des techniques d'encapsulation protégeant les principes actifs extraits de plantes comme le Resvératrol, le Bêta-carotène, et la Curcumine seront réalisées. Quatre types de synthèse seront respectivement utilisés : la micro-encapsulation , la nanoémulsion, et la synthèse de nanoparticules solides lipidiques (SLN), ainsi que la squalénisation.Une comparaison des effets anti-inflammatoires des traitements conventionnels versus les vecteurs synthétisés au cours de cette étude pourra permettre de conclure sur la contribution originale de ce projet. / For the last fifty years, the incidence of Crohn's disease, a chronic inflammatory bowel disease (IBD) has more than doubled. It is a multifactorial and idiopathic pathology using treatments such as anti-inflammatories, corticosteroids, immunosuppressants and more recently anti-TNFα.They have limits with intolerance to active principles and resistance to treatment leading to therapeutic failure . The goal of this work will be to develop an oral form while minimizing the risk of side effects by improving bioavailability. Encapsulation techniques protecting the active ingredients extracted from plants such as Resveratrol, Beta-carotene, and Curcumin will be performed. Four types of synthesis will be used respectively: micro-encapsulation, nanoemulsion, and the synthesis of lipid solid nanoparticles (SLN), as well as squalenization. A comparison of the anti-inflammatory effects of conventional treatments versus the vectors synthesized during this study. The study may conclude on the original contribution of this project.

Made available in DSpace on 2014-12-17T14:03:31Z (GMT). No. of bitstreams: 1 JaniceSC.pdf: 2257338 bytes, checksum: 87ae25d4af8c910f8c675e38f8bfe103 (MD5) Previous issue date: 2005-04-08 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Berberine is an alkaloid used as a fluorochrome in the identification of heparin and DNA. Enerback, 1974, described the technique used until today to study granules rich in heparin of vertebrate mast cells. Santos et al., 2003, studied mast cells of the mollusk Anomalocardia brasiliana using biochemical and histological analysis. This work used the fluorescent dye berberine technique to improve characterization of these cells. Mollusk organs (ctenidium and mantle) were processed with routine histological techniques. Tissue sections were treated with berberine 0,02% in redistilled water acidified to pH 4, by the addition of citric acid for 20 minutes. The visualization was made through fluorescence microscopy with ultraviolet region emission. The mast cell fluorescence had a strong yellow color, where cell nuclei appeared more greenish. This result was very similar to the ones reported before. Mast cells are location at the epithelium surface is the same in both organs, mantle and ctenidium. The fluorescence was easily observed in the granules. Therefore, this technique showed to be good and sensitive to study mast cell of invertebrates / A berberina ? um alcal?ide usado como fluorcromo na identifica??o de heparina e DNA. Enerb?ck, em 1974, descreveu a t?cnica at? hoje empregada deste fluorcromo no estudo dos gr?nulos ricos em heparina dos mast?citos de vertebrados. Santos et al., em trabalhos anteriores, utilizando abordagens bioqu?mica e histol?gica, descreveram a presen?a de mast?citos no marisco Anomalocardia brasiliana. Baseado nestes estudos, testamos a t?cnica de fluoresc?ncia com berberina para a caracteriza??o adicional dessas c?lulas. Destarte, mantos e cten?deos dos esp?cimes foram submetidos a t?cnicas rotineiras de fixa??o e inclus?o em parafina. Os cortes histol?gicos foram desparafinados, hidratados e incubados com cloridrato de berberina (0,02%) em ?cido c?trico (1%) por 20 minutos, sendo o excesso retirado com ?cido c?trico (pH 4) por 5 minutos. A visualiza??o das se??es foi feita por microscopia de fluoresc?ncia com emiss?o no espectro ultravioleta. Pudemos evidenciar c?lulas com conte?do citoplasm?tico fluorescente amarelo-brilhante, correspondentes ?quelas descritas anteriormente como mast?citos, localizadas nos epit?lios dos ?rg?os. Algumas esp?cimes, logo ap?s a disseca??o foram submetidas a tratamento com desgranulantes e depois processadas como citado acima. O uso da fluoresc?ncia tornou mais f?cil a delimita??o do conte?do granular destas c?lulas em rela??o ao n?cleo (que emite fluoresc?ncia esverdeada). Sendo assim, a t?cnica apresentada mostrou ser bastante sens?vel e promissora para o estudo dos mast?citos de invertebrados

A brief summary of the use of palladium as a catalyst, the characteristic reactivity of palladium complexes and the commonly used palladium-catalysed cross coupling reactions is given, with a special focus on the palladium-catalysed α-arylation of enolates and its application to the synthesis of aromatic heterocycles. The synthesis of aromatic heterocycles via both traditional methods and more recent metal-catalysed approaches is discussed in the context of isoquinolines. The palladium-catalysed oxidation of dihydrofurans bearing an ortho-bromophenyl group at the 2-position to the corresponding 2-phenyl furans is disclosed along with some preliminary mechanistic investigations. A novel synthetic route to isoquinolines is detailed involving the palladium-catalysed α-arylation of ketone enolates with an appropriate ortho-substituted aryl halide to furnish a protected 1,5-dicarbonyl intermediate. The versatility of these intermediates is demonstrated with their conversion into isoquinolines, isoquinoline N-oxides and naphthols. The scope of the synthetic procedure is fully exemplified across more than 30 different scaffolds covering the full spectrum of electron-rich to electron-deficient moieties. The intermediates were shown to be amenable to functionalisation with electrophiles, leading to isoquinolines bearing additional substitution at the C4 position. Sequential one-pot procedures were developed allowing three and four component couplings to directly deliver highly-substituted isoquinolines from commercially available starting materials. This methodology was utilised in the total synthesis of the natural product berberine in 26% overall yield and a longest linear sequence of six steps.

Herbs have been used for many centuries in diverse civilizations for the treatment of heart disease. Only a few natural supplements claim to have direct cardiovascular actions including hawthorn (Crataegus spp.) and berberine derived from the Berberidaceae family. Several different studies indicate important cardiovascular effects of hawthorn and berberine. For example, both exert positive inotropic effects and have been used in the treatment of congestive heart failure. Recently, it was shown that hawthorn extract preparations cause negative chronotropic effects in a cultured neonatal murine cardiomyocyte assay independent of beta-adrenergic receptor blockade. The aim of this study was to further characterize the effect of hawthorn extract to decrease the contraction rate of cultured cardiomyocytes. We hypothesized that hawthorn extract may be acting through muscarinic receptors to decrease contraction rate of cardiomyocytes. Atrial and ventricular cardiomyocytes were treated with hawthorn extract in the presence of atropine or himbacine. Changes in the contraction rate of cultured cardiomyocytes revealed that both muscarinic antagonists significantly attenuated the negative chronotropic activity of hawthorn extract. Using quinuclidinyl benzilate, L-[benzylic-4,4'-3H] ([³H]-QNB) as a radioligand antagonist, the effect of a partially purified hawthorn extract fraction to inhibit muscarinic receptor binding was quantified. Hawthorn extract fraction 3 dose-dependently inhibited [³H]-QNB binding to mouse heart membranes. These findings suggest that muscarinic receptors may be involved in the negative chronotropic effect of hawthorn extracts in neonatal murine cardiomyocytes. Berberine exhibits variable positive and negative chronotropic effects in different species. Our first aim was to examine the effect of berberine in a cultured neonatal murine cardiomyocyte assay. Our study demonstrates that berberine has significant negative chronotropic actions on cardiomyocytes which is not an effect of beta-adrenergic receptor blockade. Pertussis toxin (PTX), a Gi/o protein inhibitor, blocked the negative chronotropic activity of berberine. Muscarinic, adenosine, opioid, and α₂ receptors are coupled through a G-protein (Gi/o) to adenylyl cyclase in an inhibitory fashion. Activation of these receptors are primarily responsible for PTX-sensitive negative chronotropic effects in heart. We hypothesized that berberine may be acting through one of these receptor type to decrease contraction rate of cardiomyocytes. For this purpose, we studied the effects of the muscarinic-receptor antagonists, atropine, himbacine, or AF- DX 116 on the negative chronotropic activity of berberine. Muscarinic antagonists completely blocked the effect of berberine on contraction rate of cardiomyocytes, whereas the bradycardic effect of berberine was not inhibited by the opioid, adenosine, or α2 receptor antagonists naloxone, CGS 15943, or phentolamine, respectively. Using [³H]QNB as a radioligand, we demonstrated that berberine bound to muscarinic receptors of adult mouse heart membranes with relatively high affinity. Furthermore, berberine dose-dependently inhibited [³H]QNB binding to muscarinic M2 receptors exogenously expressed in HEK 293 cells. Therefore, the findings of the present study suggest that berberine has muscarinic agonist effects in cultured neonatal murine cardiomyocytes, potentially explaining reported physiological effects of berberine. Cardiac hypertrophy represents the most important factor in the development of congestive heart failure. We investigated the inhibitory effect of berberine on hypertrophy of H9c2 cells. In rat heart-derived H9c2 myoblast cells treated with different hypertrophic agonists such as insulin growth factor II (IGF-II), arginine vasopressin (AVP), phenylephrine, and isoproterenol, protein content and size of cells were significantly increased compared to control group. However, the number of H9c2 cells after treatment with hypertrophic agonists did not differ significantly compared to control. The increases in area of cells and protein content induced by the hypertrophic agonists were inhibited by treatment with berberine in a concentration-dependent manner. Our findings have provided the first scientific evidence that berberine may have an inhibitory effect on hypertrophy of heart-derived cells, and provide a rationale for further studies to evaluate berberine's cardiac activity. / Graduation date: 2010