Several trace metals have been shown to modify cell injury as indicated by reduction of observable pathological tissue changes after metal ion supplementation. An example of this is zinc ion induced protection against some of the liver injury caused by a single injection of carbon tetrachloride (CCl₄) to male Sprague-Dawley rats. Carbon tetrachloride liver injury is associated with membrane labilization as indicated by lysosomal and endoplasmic reticulum anomalies. Depressed hepatic levels of NADPH are observed during CCl₄ poisoning. Lipid metabolism is also impaired due to CCl₄ administration to animals. These biochemical manifestations of CCl₄ hepatotoxicity were studied in the presence of zinc ions in order to understand the mechanisms of the zinc protective effect against CCl₄ injury. The effect of zinc ions on the stability of rat liver lysomes was studied. Zinc was added by several methods: (1) feeding the animals a high zinc diet, (2) infusion of zinc into the liver in situ through the portal vein, or (3) by adding zinc to the lysosomal fraction either before or after isolation of this fraction from rat liver homogenates. By all techniques, addition of zinc reduced the release of β-glucuronidase from liver lysosomes, indicating increased stability of the suborganelles. The zinc induced protection against CCl₄ liver damage was evident in observations made using both light microscopy and electron microscopy. The increased release of lysosomal β-glucuronidase observed in the CCl₄ treated rats was significantly reduced by zinc administration. Also, decreases in microsomal protein synthesis and seromucoid levels due to the CCl₄ treatment were significantly ameliorated by zinc. Thus, disruption of lysosomal and endoplasmic reticulum membranes, one of the earliest signs of CCl₄ hepatotoxicity, appeared to be inhibited by pretreating the animals with zinc chloride. Depressed hepatic levels of NADPH are observed in rats administered CCl₄. Zinc chloride pretreatment of these rats significantly increased the NADPH levels in the liver. Since zinc ions bind NADPH, then the protective effect of zinc against CCl₄ toxicity may be due to stabilization of the pyridine nucleotide by zinc and the subsequent prevention of CCl₄ induced alterations of biochemical reactions dependent upon NADPH. Zinc chloride pretreatment of CCl₄ treated rats significantly reduced the CCl₄ induced hepatic triacylglycerol accumulation. Concomitant with this event is the appearance of elevated levels of newly synthesized triacylglycerols in the serum of the CCl₄ treated rats given zinc above that of the CCl₄ treated rats. Hepatic triacylglycerol synthesis is unchanged by CCl₄ or zinc treatment. Hepatic phospholipid levels which are depressed by the CCl₄ hepatotoxin are not affected by zinc treatment. However, the synthesis of phospholipids in the livers of rats treated with CCl₄ plus zinc is significantly increased. The lipid changes induced by CCl₄ and zinc dosing of rats are indicative of alterations in liver membranes thus affecting hepatic liver transport mechanisms. On the basis of the data presented, the effects of zinc ions on CCl₄ hepatotoxicity are discussed and applied to understanding the regulating role of metal ions in tissue injury. The protective effects of zinc ions against CCl₄ hepatotoxicity suggest a relationship between the zinc nutritional status of animals exposed to environmental contaminants, and the expression of the ensuing tissue damage.

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.

O uso de tetracloreto de carbono (CCl4) em ratos é um modelo experimental de dano ao tecido hepático, desencadeando fibrose e, a longo prazo, cirrose. Seu metabolismo ocorre no fígado pelo citocromo P450, resultando na produção de radicais livres e estimulação da lipoperoxidação, que induz um processo de necrose, inflamação e maior progressão da fibrose. Vários antioxidantes, entre eles os flavonoides, têm sido referidos como eficazes para diminuir a fibrose em modelos animais. Este estudo pretende avaliar a ação antioxidante da quercetina (Q) em um modelo experimental de cirrose induzida por CCl4 inalatório. Foram utilizados 25 ratos Wistar machos, com peso médio de 250g, divididos em 3 grupos: Controle (CO), CCl4 e CCl4+Q. Os ratos foram submetidos a inalações de CCl4 (2x/semana), durante 16 semanas, recebendo fenobarbital na água de beber na dose de 0,3g/dl, como indutor enzimático. A Q (50mg/Kg) via intraperitoneal foi iniciada na 10ª semana de inalação, perdurando até o final do experimento. A análise estatística foi ANOVA, seguida de Student Newmann Keuls (Média±SEM), considerando-se diferença estatisticamente significativa quando p<0,05. Após o tratamento com quercetina, observamos uma melhora na integridade hepática, diminuição da fibrose, do conteúdo de colágeno e re-estabelecimento nos níveis dos metabólitos do óxido nítrico, comparado ao grupo CCl4. Constatou-se também redução do dano oxidativo, verificada pela diminuição das substâncias que reagem ao ácido tiobarbitúrico (TBA-RS), assim como aumento na atividade das enzimas antioxidantes e da relação GSH/GSSG. A partir desses dados, sugerimos que o emprego da quercetina possa ser promissor como terapia antioxidante nas complicações hepáticas. / Carbon tetrachloride (CCl4) is a classic experimental model of oxidative damage to liver tissue, causing long-term fibrosis and cirrhosis. Metabolism in the liver via cytochrome P450 results in the stimulation of lipid peroxidation and production of free radicals, which induce a process of necrosis, inflammation and greater progression of fibrogenesis. Various antioxidants and flavonoids have been identified as effective in reducing fibrosis in animal models. This study aimed to assess the antioxidant activity of quercetin (Q) in an experimental model of cirrhosis induced by CCl4 inhalation. We used 25 male Wistar rats (250g) that were divided into 3 groups: control (CO), CCl4 and CCl4 + Q. The rats were subjected to CCl4 inhalation (2x/week) for 16 weeks, and they received phenobarbital in their drinking water at a dose of 0.3 g/dl as a P450 enzyme inducer. Q (50 mg/Kg) was initiated intraperitoneally at 10 weeks of inhalation and lasted until the end of the experiment. Statistical analysis was by ANOVA Student-Newman Keuls (mean ± SEM), and differences were considered statistically significant when p <0.05. After treatment with quercetin, we observed an improvement in liver integrity, decreased fibrosis, as analyzed by picrosirius for the quantification of collagen, and restored levels of nitric oxide metabolites compared with the CCl4 group. It also reduced oxidative stress, as confirmed by the decrease of substances reacting to thiobarbituric acid (TBARS), the increased activity of antioxidant enzymes and the reduced glutathione ratio and glutathione disulfide (GSH/GSSG). From these data, we suggest that the use of quercetin might be promising as an antioxidant therapy in liver complications.

O uso de tetracloreto de carbono (CCl4) em ratos é um modelo experimental de dano ao tecido hepático, desencadeando fibrose e, a longo prazo, cirrose. Seu metabolismo ocorre no fígado pelo citocromo P450, resultando na produção de radicais livres e estimulação da lipoperoxidação, que induz um processo de necrose, inflamação e maior progressão da fibrose. Vários antioxidantes, entre eles os flavonoides, têm sido referidos como eficazes para diminuir a fibrose em modelos animais. Este estudo pretende avaliar a ação antioxidante da quercetina (Q) em um modelo experimental de cirrose induzida por CCl4 inalatório. Foram utilizados 25 ratos Wistar machos, com peso médio de 250g, divididos em 3 grupos: Controle (CO), CCl4 e CCl4+Q. Os ratos foram submetidos a inalações de CCl4 (2x/semana), durante 16 semanas, recebendo fenobarbital na água de beber na dose de 0,3g/dl, como indutor enzimático. A Q (50mg/Kg) via intraperitoneal foi iniciada na 10ª semana de inalação, perdurando até o final do experimento. A análise estatística foi ANOVA, seguida de Student Newmann Keuls (Média±SEM), considerando-se diferença estatisticamente significativa quando p<0,05. Após o tratamento com quercetina, observamos uma melhora na integridade hepática, diminuição da fibrose, do conteúdo de colágeno e re-estabelecimento nos níveis dos metabólitos do óxido nítrico, comparado ao grupo CCl4. Constatou-se também redução do dano oxidativo, verificada pela diminuição das substâncias que reagem ao ácido tiobarbitúrico (TBA-RS), assim como aumento na atividade das enzimas antioxidantes e da relação GSH/GSSG. A partir desses dados, sugerimos que o emprego da quercetina possa ser promissor como terapia antioxidante nas complicações hepáticas. / Carbon tetrachloride (CCl4) is a classic experimental model of oxidative damage to liver tissue, causing long-term fibrosis and cirrhosis. Metabolism in the liver via cytochrome P450 results in the stimulation of lipid peroxidation and production of free radicals, which induce a process of necrosis, inflammation and greater progression of fibrogenesis. Various antioxidants and flavonoids have been identified as effective in reducing fibrosis in animal models. This study aimed to assess the antioxidant activity of quercetin (Q) in an experimental model of cirrhosis induced by CCl4 inhalation. We used 25 male Wistar rats (250g) that were divided into 3 groups: control (CO), CCl4 and CCl4 + Q. The rats were subjected to CCl4 inhalation (2x/week) for 16 weeks, and they received phenobarbital in their drinking water at a dose of 0.3 g/dl as a P450 enzyme inducer. Q (50 mg/Kg) was initiated intraperitoneally at 10 weeks of inhalation and lasted until the end of the experiment. Statistical analysis was by ANOVA Student-Newman Keuls (mean ± SEM), and differences were considered statistically significant when p <0.05. After treatment with quercetin, we observed an improvement in liver integrity, decreased fibrosis, as analyzed by picrosirius for the quantification of collagen, and restored levels of nitric oxide metabolites compared with the CCl4 group. It also reduced oxidative stress, as confirmed by the decrease of substances reacting to thiobarbituric acid (TBARS), the increased activity of antioxidant enzymes and the reduced glutathione ratio and glutathione disulfide (GSH/GSSG). From these data, we suggest that the use of quercetin might be promising as an antioxidant therapy in liver complications.

No description available.

Yang Lei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 141-148). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Abstract (Chinese Version) --- p.iv / Table of Contents --- p.vi / List of Abbreviations --- p.xii / List of Figures --- p.xiii / List of Tables --- p.xviii / Chapter Chapter 1 --- Literature review --- p.1 / Chapter 1.1 --- Carbon tetrachloride (CC14) --- p.1 / Chapter 1.2 --- Major uses of CC14 --- p.1 / Chapter 1.3 --- Potential human exposure pathways to CC14 --- p.2 / Chapter 1.4 --- Toxicity of CC14 --- p.3 / Chapter 1.5 --- Mechanism of CCl4-induced hepatotoxicity --- p.5 / Chapter 1.6 --- Role of CYP2E1 involved in CCl4-induced hepatotoxicity --- p.7 / Chapter 1.7 --- Definite proof of the involvement of CYP2E1 in CCl4-induced hepatotoxicity by CYP2El-null mouse in vivo model --- p.10 / Chapter 1.8 --- Identification of CYP2E1 -dependent genes involved in CCl4-induced hepatotoxicity by fluorescent differential display (FDD) --- p.11 / Chapter 1.9 --- Objectives of the study --- p.14 / Chapter Chapter 2 --- Materials and methods --- p.16 / Chapter 2.1 --- Animals and treatments --- p.16 / Chapter 2.1.1 --- Materials --- p.16 / Chapter 2.1.2 --- Methods --- p.16 / Chapter 2.2 --- Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) analyses --- p.17 / Chapter 2.2.1 --- Materials --- p.17 / Chapter 2.2.2 --- Methods --- p.17 / Chapter 2.2.2.1 --- Serum preparation --- p.17 / Chapter 2.2.2.2 --- Activity determination --- p.18 / Chapter 2.3 --- Tail-genotyping by PCR --- p.18 / Chapter 2.3.1 --- Materials --- p.18 / Chapter 2.3.2 --- Methods --- p.20 / Chapter 2.3.2.1 --- Preparation of genomic DNA from mouse tail --- p.20 / Chapter 2.3.2.2 --- PCR reaction --- p.20 / Chapter 2.4 --- Total RNA isolation --- p.21 / Chapter 2.4.1 --- Materials --- p.21 / Chapter 2.4.2 --- Methods --- p.21 / Chapter 2.5 --- DNase I treatment --- p.23 / Chapter 2.5.1 --- Materials --- p.23 / Chapter 2.5.2 --- Methods --- p.23 / Chapter 2.6 --- Reverse transcnption of mRNA and amplification by fluorescent PCR amplification --- p.26 / Chapter 2.6.1 --- Materials --- p.27 / Chapter 2.6.2 --- Methods --- p.27 / Chapter 2.7 --- Fluorescent differential display (FDD) --- p.28 / Chapter 2.7.1 --- Materials --- p.28 / Chapter 2.7.2 --- Methods --- p.28 / Chapter 2.8 --- Excision of differentially expressed cDNA fragments --- p.29 / Chapter 2.8.1 --- Materials --- p.29 / Chapter 2.8.2 --- Methods --- p.29 / Chapter 2.9 --- Reamplification of differentially expressed cDNA fragments --- p.34 / Chapter 2.9.1 --- Materials --- p.34 / Chapter 2.9.2 --- Methods --- p.34 / Chapter 2.10 --- Subcloning of reamplified cDNA fragments --- p.36 / Chapter 2.10.1 --- Materials --- p.36 / Chapter 2.10.2 --- Methods --- p.37 / Chapter 2.11 --- Purification of plasmid DNA from recombinant clones --- p.39 / Chapter 2.11.1 --- Materials --- p.39 / Chapter 2.11.2 --- Methods --- p.39 / Chapter 2.12 --- DNA sequencing of differentially expressed cDNA fragments --- p.40 / Chapter 2.12.1 --- Materials --- p.40 / Chapter 2.12.2 --- Methods --- p.40 / Chapter 2.12.3 --- BLAST search against the GenBank DNA databases --- p.41 / Chapter 2.13 --- Northern blot analysis of differentially expressed cDNA fragments --- p.41 / Chapter 2.13.1 --- Formaldehyde gel electrophoresis of total RNA --- p.41 / Chapter 2.13.1.1 --- Materials --- p.42 / Chapter 2.13.1.2 --- Methods --- p.42 / Chapter 2.13.2 --- Preparation of cDNA probes for hybridization --- p.42 / Chapter 2.13.2.1 --- EcoRI digestion of cDNA inserts from plasmid DNA --- p.42 / Chapter 2.13.2.1.1 --- Materials --- p.42 / Chapter 2.13.2.1.2 --- Methods --- p.43 / Chapter 2.13.2.2 --- Purification of DNA from agarose gel --- p.43 / Chapter 2.13.2.2.1 --- Materials --- p.43 / Chapter 2.13.2.2.2 --- Methods --- p.43 / Chapter 2.13.2.3 --- DIG labeling of cDNA --- p.44 / Chapter 2.13.2.3.1 --- Materials --- p.44 / Chapter 2.13.2.3.2 --- Methods --- p.44 / Chapter 2.13.3 --- Hybridization --- p.45 / Chapter 2.13.3.1 --- Materials --- p.45 / Chapter 2.13.3.2 --- Methods --- p.45 / Chapter Chapter 3 --- Results --- p.47 / Chapter 3.1 --- Liver morphology --- p.47 / Chapter 3.2 --- Serum ALT and AST activities --- p.47 / Chapter 3.3 --- Tail-genotyping by PCR --- p.51 / Chapter 3.4 --- DNase I treatment --- p.51 / Chapter 3.5 --- FDD RT-PCR and excision of differentially expressed cDNA fragments --- p.51 / Chapter 3.6 --- Reamplification of excised cDNA fragments --- p.61 / Chapter 3.7 --- Subcloning of reamplified cDNA fragments --- p.61 / Chapter 3.8 --- DNA sequencing of subcloned cDNA fragments --- p.69 / Chapter 3.9 --- Confirmation of differentially expressed patterns by Northern blot analysis --- p.106 / Chapter 3.10 --- Temporal expression of differentially expressed genes --- p.113 / Chapter 3.11 --- Tissue distribution of differentially expressed genes --- p.117 / Chapter Chapter 4 --- Discussion --- p.125 / Chapter 4.1 --- Liver morphology and serum ALT and AST activities --- p.126 / Chapter 4.2 --- Identification of CYP2E1 -dependent genes involved in CCl4-induced hepatotoxicity --- p.127 / Chapter 4.3 --- Functional roles of the identified differentially expressed genes --- p.129 / Chapter 4.3.1 --- Fragment B4 --- p.129 / Chapter 4.3.2 --- Fragment C12 --- p.130 / Chapter 4.3.3 --- Fragment B13 --- p.131 / Chapter 4.3.4 --- Fragment A5 --- p.132 / Chapter 4.4 --- Temporal expression of differentially expressed genes --- p.133 / Chapter 4.4.1 --- Fragment B4 --- p.133 / Chapter 4.4.2 --- Fragment C12 --- p.134 / Chapter 4.4.3 --- Fragment B13 --- p.134 / Chapter 4.4.4 --- Fragment A5 --- p.135 / Chapter 4.5 --- Tissue distribution of differentially expressed genes --- p.136 / Chapter 4.5.1 --- Fragment B4 --- p.136 / Chapter 4.5.2 --- Fragment C12 --- p.136 / Chapter 4.5.3 --- Fragment B13 --- p.137 / Chapter 4.5.4 --- Fragment A5 --- p.137 / Chapter 4.5.5 --- Roles of the identified genes involved in CCl4-induced hepatotoxicity --- p.138 / Chapter 4.6 --- Normalization of Northern blot analysis --- p.13 8 / Chapter 4.7 --- Limitations of FDD technique to identify differentially expressed genes --- p.138 / Chapter 4.8 --- Future studies --- p.139 / Chapter 4.8.1 --- Investigation of the differential expression patterns of the identified genes in acetaminophen-induced liver injury --- p.139 / Chapter 4.8.2 --- Dot blot analysis --- p.140 / Chapter 4.8.3 --- DNA microarray --- p.140 / References --- p.141

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

No description available.

Ácidos graxos conjugados (AGCs) é o termo geral para descrever os isômeros posicionais e geométricos dos ácidos graxos poliinsaturados com duplas ligações conjugadas. Inúmeros efeitos benéficos para a saúde como: anti-cancerígeno, anti-aterogênicos, anti-adipogênicos e anti-inflamatórios, tem sido atribuídos ao consumo dos AGCs. Entretanto, estudos sobre os efeitos dos AGCs no organismo ainda são inconclusivos e por isso o interesse em pesquisas visando a sua participação em processos fisiológicos. O objetivo deste estudo foi avaliar em ratos o efeito dos isômeros conjugados do ácido linoleico (9cis, 11trans e 10trans, 12cis) sobre o perfil lipídico tecidual e sua influência sobre parâmetros bioquímicos em processos oxidativos. Não foi possível detectar a atividade antioxidante in vitro dos CLAs. Os resultados obtidos demonstraram que o FFA-CLA foi capaz de reagir apenas com o radical DPPH. No experimento in vivo uma mistura comercial dos isômeros (9cis, 11trans e 10trans, 12 cis) foi utilizada como fonte de CLAs, e a influência da suplementação desses isômeros, foi avaliada e comparada com um grupo controle suplementado com água e com grupos experimentais suplementados com óleo de soja. O primeiro experimento foi realizado com animais Wistar saudáveis e teve duração de 40 dias, as amostras de ácidos graxos livres de CLAs, (FFACLAs) e óleo de soja foram fornecidas aos animais por meio de entubação orogástrica nas concentrações de 1%, 2% e 4% em relação ao consumo diário de dieta, o grupo controle recebeu 1% de água. A suplementação da dieta dos animais com os CLAs leva ao aumento nos níveis de triglicérides, mas não interfere nos parâmetros de estresse oxidativo, embora haja incorporação dose-dependente nos tecidos hepático, muscular e adiposo, não foram observadas alterações no volume das células adiposas, e na área e diâmetro do tecido muscular. No segundo experimento, com duração de 21 dias, ao avaliar o efeito da suplementação na dose de 2% de CLAs em ratos Wistar induzidos a peroxidação, pelo tratamento com tetracloreto de carbono. Pôde-se observar efeitos hepatoprotetor, dos CLAs atribuídos a sua prevenção na peroxidação lipídica e ao aumento da atividade das enzimas catalase (CAT), glutatina redutase (GR) e glutationa reduzida (GSH). / Conjugated fatty acids (CFAs) is the general term to describe positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds. Many beneficial health effects such as anti-cancer, anti-atherogenic, anti-adipogenic and anti-inflammatory, has been attributed to the consumption of the CFAs. However, studies on the effects of the CFAs in the body are still inconclusive and therefore the interest in research aimed at their participation in processes physiological. The objective of this study was to evaluate in rats the effect of conjugated linoleic acid isomers (9cis, 11trans and 10trans, 12cis) on lipid profile tissue and its effect on biochemical parameters in oxidative processes. It was not possible to detect the in vitro antioxidant activity of CLAs. The results showed that the free fatty acids of CLAs (FFA-CLAs) was able to react only with the DPPH radical. In in vivo experiment a commercial mixture of isomers (9cis, 11trans and 10trans, 12cis) was used as a source of CLAs and the influence of supplementation of these isomers was evaluated and compared with a control group supplemented with water and experimental groups supplemented with soybean oil. The first experiment was conducted with healthy Wistar and lasted 40 days, samples of FFA-CLA and soybean oil were delivered to animals via orogastric intubation at concentrations of 1%, 2 % and 4% in relation to daily diet, the control group received 1% water. Supplementing the diet with CLAs leads to increased levels of triglycerides, but does not interfere with oxidative stress parameters, although there is a dose-dependent incorporation into liver tissue, muscle and fat, no changes were observed in the volume of fat cells, and in the area and diameter of muscle tissue. In the second experiment, lasting 21 days, to evaluate the effect of supplementation at a dose of 2% of CLAs in Wistar, tha peroxidation induced by treatment with carbon tetrachloride. Could be observed hepatoprotective effects, attributed to the CLAs prevention lipid peroxidation and increased activity of the enzymes catalase (CAT), glutathione reductase (GR) and glutathione reduzida (GSH).