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This thesis records my investigations into the consequences of overdosage with the analgesic drug paracetamol. The major complication, that of hepatic necrosis, has been investigated in experimental animals using light-microscopy, electron-microscopy and histochemistry. The pathological findings in 18 fatal human cases are recorded and compared and contrasted with previous reports in the literature. A further 16 fatalities resulting from overdosage with compound preparations containing paracetamol are also reported. A variety of methods for quantifying the extent of hepatic necrosis have been evaluated, including the use of the image-analysis computer, and these methods applied to experimental and human material. In addition to morphological studies, the influence of microsomal induction on the toxic metabolism of the drug has been investigated and the effectiveness of a possible antidote, a tocopherol, has been tested in the rat. The thesis includes chapters on the history and usage of paracetamol and on the treatment of overdosage based on reviews of the literature.

TRAIL (TNF-Related Apoptosis-Inducing Ligand) and its receptors represent a relatively new and poorly characterised subset of the TNF family. The transcription factor NF-kappaB is an important cellular survival pathway and its potential activation by TRAIL was assessed. TRAIL activates NF-kappaB only in TRAIL resistant cells whereas activation was only observed in sensitive cells in the presence of a caspase inhibitor suggesting a caspase-sensitive component. NF-kappaB activation could regulate TRAIL cytotoxicity as its inhibition in resistant cells led to them becoming sensitive to TRAIL while activation in sensitive cells made these cells refractory to TRAIL. The native TRAIL DISC (Death-Inducing Signalling Complex) was characterised and found to contain FADD (Fas-Associated Death Domain Protein) and the inhibitor caspases-8 and -10. FADD- and caspase-8-deficient cells were refractory to TRAIL-induced apoptosis indicating an obligatory role for these components in TRAIL signalling. DISCs were formed irrespective of the TRAIL sensitivity of the cell. Consistent with TRAIL activating NF-kappaB, RIP (Receptor Interacting Protein), a protein required for TNF-mediated NF-kappaB activation, was present within the DISC. Analysis of the native TNF-R1 signalling complex revealed the presence of proteins required for NF-kappaB activation, RIP and TRAF2 (TNF-Associated Factor 2) however the apoptotic mediators, namely FADD and caspase-8 were absent despite being required for apoptosis induction. Finally, others have reported that protein kinase C (PKC) activation can protect cells from death receptor apoptosis. PMA (Phorbol Myristate Acetate)-mediated PKC activation protected HeLa cells from TRAIL-induced apoptosis. DISC analysis revealed that PKC activation modulated apoptosis by inhibiting FADD recruitment.

Quinone based drugs are complex structures with multiple chemical properties. Therefore in this work to further understand quinone toxicity in drugs simpler structures with defined chemistry were used as tools. To discern mechanistic insight transcriptomic investigations were undertaken in rat hepatocytes and in vivo mouse liver exposed to a range of prototypical quinines. Genes important in response to quinone exposure were identified and analysed using several bioinformatic tools. Transcriptomics in hepatocytes could not differentiate quinone redox effects from other interactions, although 22 'quinone signature genes' indicated a coordinated response to redox stress. A central role for mitochondria as targets of quinone interaction was confirmed, the transcriptomic profile indicating optimisation of energy metabolism and suppression of intrinsic apoptosis. Pim1 and Pim3 kinases were central to this response, confirmed in follow up experiments. Pharmacokinetics from mice treated in vivo with 25mg/kg DMNQ or menadione interperitoneally indicated DMNQ to be more widely distributed and better suited as an in vivo redox model compound than menadione. However, in vivo redox challenge from DMNQ in the liver was transient and insufficient to cause oxidative damage. The findings indicate that DMNQ has utility for studying redox stress in vivo, although a repeat dosing approach is required in future. The findings add to the knowledge-base of quinone toxicity. Particularly the increased responsiveness and sensitivity of hepatocytes in vitro compared to in vivo which may lead to an erroneous perception of toxicity if in vitro systems are studied alone.

Nicotinic acetylcholine receptors (nAChRs) are widely present in the central nervous system (CNS). However, their cellular functions and physiological significance are not yet fully understood. Recently, in vivo and in vitro studies have suggested a possible neuroprotective role for nAChRs. Exposure to nicotine, an agonist at nAChRs, has been shown to protect from neurotoxicity induced by NMDA, glutamate and potassium withdrawal, and to prevent beta-amyloid induced neurotoxicity. Furthermore, stimulation of nAChRs has been shown to delay the ageing process of nigrostriatal neurons, increase neurotrophic factor levels and up-regulate the expression of NGF receptors in the brain. These observations may provide a basis for the findings that cigarette smoking is negatively correlated with Parkinson's disease and positively correlated with the delayed onset of Alzheimer's disease (AD). In conjunction with this, nicotine has been shown to affect a wide variety of biological functions including gene expression.;As nAChRs are calcium permeable channels, we have focused this current study on the effect of nicotine on the regulation of cellular proteins responsible for calcium-mobilisation, -transportation and -buffering. We found that in cortical neurons treated with 10microM nicotine for 24 h there is a selective up-regulation of ryanodine receptor 2 (RyR2), a calcium release channel present in the endoplasmic reticulum. In contrast, the expression of the other calcium-transporting and calcium-binding proteins tested were not affected. In nicotine treated cortical neurons, the increase RyR number was mirrored by a significant modification of the calcium response upon ryanodine stimulation.;In conclusion, our data show for the first time the effect of nicotine on the expression of proteins involved in calcium homeostasis.

There is concern about increased nitrate levels in drinking water due to potential impacts on human health. At the same time there are also concerns about the environmental impact of increased levels of nitrate in surface water systems; the increased amount of nitrate in surface water can cause eutrophication. It has become almost axiomatic that nitrate which comes from agriculture soils is one of the main drivers of the increased nitrate levels in water. Arable agriculture is considered to be one of the main sources of nitrate due to high rates of nitrogen fertiliser or manure application, non-synchronous application of fertiliser with crop demand and inappropriate management of soil and water. Therefore minimise nitrate losses from agriculture soils could help to reduce nitrate level in ground and surface waters. This PhD study aims to improve the recommendations that are available to farmers to minimise nitrate leaching from arable rotations under UK conditions by investigating the impact of typical agricultural management practices on the risks of nitrate leaching in crop rotations with potatoes and cereals. In the conclusion, the achievements of this PhD study are evaluated with reference to the original aims and objectives. Then recommendations for further work to develop the understanding of nitrate leaching in arable rotations are made.

A cohort study was carried out to investigate mortality of 1292 male painters who had worked in a Royal Naval dockyard in Scotland for at least one year during 1950 and 1992. The mortality of the painters were compared to that of general male population of Scotland in 5-year ages and 5-year periods. Among the cohort there were 205 deaths, 58 from cancer. Proportionate mortality ratios suggested elevated risks of death from all cancers (PMR=110, 95%CI 84-143), prostate cancer (225, 83-489), bladder cancer (219, 60-560) and lymphosarcoma and reticulosarcoma (769, 93-2780). Excess deaths also were found from the central nervous system disease (221, 46-645) and ischaemic heart disease (132, 105-164). Standardised mortality ratios from a subcohort of painters born in 1900 and 1929 showed a similar mortality pattern for 123 deaths: SMR for all cancers was 122 (88-165), cancer of lung 112, (64-182), prostate 263, (97-573), bladder 305, (83-782). 953 surviving painters from the dockyard cohort and 953 controls (non-painters randomly selected from the local population) were invited to participate in a questionnaire study of neuropsychological symptoms. In all, 259 painters and 529 controls took part, a practical 56.6% response. The questionnaire included occupational, smoking and alcohol histories, neuropsychological symptoms, and a personality inventory. A significant excess of symptoms was found among painters over controls. The ORs for painters with a high score (12-22) for all neuropsychological symptoms were 2.73 (0.92-8.17) for 1-4 years of exposure, 6.35 (1.66-24.31) for 5-9 years, 7.34 (1.84-29.31) for 10-14 years and 10.22 (2.53-41.20) for 15-41 years, compared with controls after adjustment for age, educational level, smoking, alcohol, neuroticism and social conformity. In multivariate analyses of subjects with high scores against those with lower scores, besides painting exposure and its dose response, smoking was associated with symptoms: OR for psychological symptoms was 1.47, 0.95-2.29 and OR for neurological symptoms was 2.59, 1.39-4.83.

Aflatoxins (AFs) are a group of mycotoxins produced by moulds of Aspergillus genus which contaminate food commodities of tropical and sub-tropical countries. The aims of this study are to assess the extent of AF contamination of foods in the UK that originated in Asia and to identify components of Thai foods that may protect against the toxicity of AFs. Examination of 12 commercial, dried Asian foods showed that long grain rice, fragrant rice, peanuts, black beans and black pepper contained Aspergillus spp. which were identified as A. parasiticus (afiatoxigenic), A. versicolor, A. ustus, A.niger and A. ochraceus. These commodities contained undetectable AFs. Jasmine brown rice and crushed chilli contained 14.7 and 11.4 IJglkg of AFs, respectively, in the absence of Aspergillus. AFBl, the most toxigenic AFs was detected in crushed chilli (lO.7IJglkg) so Aspergillus was present at some stage of food production, particularly pre-harvest stage. Cross contamination during food processing is one of possible cause of AFs contamination in these commodities. These results indicate direct and indirect risks of exposure to AFs from these products since AFs fOlmation is possible in Aspergillus-contaminated crops and AFs can be carried throughout the food chain. Hence an alternative strategy to mitigate toxicity of ingested AFs is required. One possibility is by using food components to modulate the harm from ingested AFs by altering AF metabolism and mutagenesis. In this study, the effectiveness of the compounds in Thai culinary herb, fingerroot (Boesenbergia rotunda) were investigated. A crude methanol extract (ME) of fingerroot was analysed and found to contain ~ 15 putative flavonoids as major components of which pinocembrin, pinocembrin chalcone, cardamonin, pinostrobin, 4-hydroxypanduratin A and panduratin A were identified by HPLC and LC-MS. The ME significantly inhibited fonnation of mutagenic/carcinogenic metabolite of AFBl (AFB1-epoxide, AFBO) in a cell-free metabolic system (Model 1) and also suppressed mutagenicity of AFBl in Salmonella/microsomal assay (Model 2). These inhibitory properties of the ME might be related to its indigenous flavonoids which could modulate activities of AFB1 -metabolising enzymes (CYPIA2, 3A4). Purified flavonoids (cardamonin, apigenin, pinostrobin) were found to affect AFB 1 toxicity to some extent in both models, but their potencies were much lower than the ME particularly in the Salmonella model and evidence is provided that suggests that Reactive Oxygen Species rather than AFBO are the mutagenic entities in this assay. This also suggests that fingerroot contains effective metabolic modulators that were not identified. Consumption of fmgerroot could provide a combination of potential phytochemicals that protect against aflatoxin-mediated toxicity by altering AF metabolism at the initial stages of enzymatic activation.