Faculty of Engineering, School Process & Materials Engineering, PhD Thesis / If one were to imagine the body as a chemical processing plant, then the liver would be equated to the reactor responsible for almost all the metabolic activities of the body. There is hardly any chemical produced, secreted or regulated that the liver is not directly or indirectly responsible for, making the design of an artificial liver a daunting task for any researcher. It is currently impossible to replicate the multitude of functions of a single liver cell, even given all the knowledge and technological advances of the 21st century. An artificial liver should be able to supplement the failing functions, especially those of a detoxification nature, of an injured or diseased liver. This can be achieved by harnessing the natural capabilities of transformed hepatocytes for use in a hybrid artificial liver. Today, even with all the research currently taking place, liver transplantation is still the most common response to acute or chronic liver failure. The aim of this study was to develop a feasible theoretical design for a hybrid artificial liver reactor. This study draws on various disciplines such as biochemistry, medicine and engineering. A high-level systems approach was employed to the Process Synthesis. Process Synthesis methodology ensures efficiency in the design process which is achieved by conducting the laboratory experiments in parallel with the reactor or process design such that only those experiments or parameters that require optimisation need to be performed. The capability of the selected transformed hepatocyte cell lines, HuH7 and HepG2 for specific liver functions; the intrinsic cells kinetics for the two cell lines and the sensitivity of the reactor design to the cell line incorporated were determined. The three liver function tests selected were: ammonia metabolism, lignocaine uptake and 99mTc-DISIDA uptake. Our laboratory data demonstrate that for all three functions, both the cell lines exhibit liver functionality and that their kinetics are fairly similar. This finding suggests that the type of cell line incorporated in the reactor does not appear to significantly impact on the reactor design. Hence, it would appear from the preliminary screening tests that the choice of cell line incorporated is not a key parameter. Since Chang’s method of immuno-isolation by microencapsulation was employed, the kinetics of external mass transfer was compared to the intrinsic cell kinetics to determine the rate-limiting step. Results indicate that the capsular membrane does not significantly impede mass transfer and that intrinsic cell kinetics is the rate-limiting step. The research has demonstrated that a packed bed configuration is a feasible reactor type capable of including the

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The glutathione transferases (GSTs) of maize have been the most studied GSTs in plants, however much is still not known about these enzymes. In the course of the current study six GST subunits (Zm GSTs I, II and III, which have been reported previously, and Zm GSTs V, VI and VII, which have not been previously reported) have been identified in the dimers Zm GST I-I, I-II, I-III, V-V, V-VI and V-VII. Maize GSTs are known to be important in herbicide detoxification and the purified maize enzymes were each found to have differing activities toward a number of herbicides, and also a range of other potential GST substrates. Additionally, Zm GST I II and Zm GST V-V possessed glutathione peroxidase activity. The developmental regulation and chemical inducibility of maize GSTs were studied in maize seedlings using western blotting, with different subunits showing markedly different responses. Zm GST I was constitutively present in all plant parts and unaffected by chemical treatment, Zm GST II was only detected in young roots but was induced in roots and shoots by many different chemical treatments, and Zm GST V was present at low levels throughout maize plants, with levels enhanced greatly by treatment with the safener dichlormid but not by other chemicals tested. cDNA clones corresponding to Zm GST subunits I, III, V, VI and VII were isolated by library screening using antibody or DNA probes. The cDNA sequences for Zm GST subunits V, VI and VH were different from those of previously cloned type I (theta class) maize GSTs and were most similar to the auxin-regulated GST family (type III or tau class GSTs) previously only identified in dicotyledonous species. The cloned GSTs were expressed as recombinant proteins in E. coli, allowing further characterisation, including detailed kinetic analysis for recombinant Zm GST I-I and Zm GST V-V.

The cytochrome P-450 dependent monooxygenase activity in a 'wild type' susceptible strain of housefly was studied. Catalytic activities were identified that demonstrated that the housefly cytochrome P-450 was capable of similar catalytic functions as those described for higher animals. Although several specific activities were lower than in mammalian species, benzphetamine N-demethylation was comparable and there was higher constitutive activity toward lauric acid than is observed in rat hepatic microsomes. The inducing agent phenobarbital increased both total cytochrome P-450 content and the benzphetamine N-demethylase specific activity. The high constitutive activity for fatty acids was induced by the hypolipidaemic drug clofibrate, specifically inducing the w-hydroxylase activity. The substrate specificity toward lauric acid extended equally to myristic and palmitic acid. Housefly microsomal cytochrome P-450 also metabolised the unsaturated fatty acid, arachidonic acid, the w-hydroxy-lation again inducible by clofibrate pretreatment. The w-hydroxylation of these fatty acids appeared to be a well-coupled reaction, a property that also appeared to be exhibited by the rat hepatic w-hydroxylase. The housefly fatty acid hydroxylation showed certain similarities to that in the rat, both in the specificity for w-hydroxylation and in the result of induction by clofibrate. Structural comparison to cytochrome P-450IVA1, IIB1 and IA1 was made by Western blot analysis with polyclonal antibodies raised to these rat hepatic isoenzymes. Housefly cytochrome P-450 shared few, if any, common epitopes with these rat isoenzymes, nor did these antibodies inhibit housefly cytochrome P-450 dependent monooxygenase activity. Cytochrome P-450 from clofibrate-pretreated housefly microsomes was partially purified by affinity chromatography. The cytochrome P-450 had a specific content of 5. 7nmol.mg-1 and a monomeric molecular weight of 52,000 daltons and a reduced carbon monoxide difference spectrum absorbance maxima at 448nm. In a reconstituted system, this preparation exhibited activity toward lauric acid and to a lesser extent arachidonic acid in each case w-hydroxylated products predominated. This is the first example of a purification of an insect cytochrome P-450 multiple form with a defined product reaction.

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KefB and KefC are glutathione-gated potassium channels that play a protective role during the detoxification of electrophiles in Gram negative bacteria. The KefC channel from Klebsiella aerogenes has been characterised and the gene cloned and sequenced. The KefC channel from K. aerogenes is analogous to KefC from Escherichia coli. The electrophile compounds NEM and CDNB are strong activators of potassium loss via the channel, whereas, methylglyoxal is a weak activator of potassium loss. At the amino acid level the putative protein shows a high degree of similarity with KefC from E. coli. While sequencing the kefC gene from K. aerogenes a difference in the genome organisation of K. aerogenes and E. coli was observed, highlighting the presence of an unassigned ORF, yabF, that overlaps the kefC by 8 bp. Clones of the K. aerogenes kefC gene that lack the first 129 bp of yabF exhibit reduced KefC activity. Analysis of the sequence surrounding the kefB gene from E. coli revealed an ORF, yhaH, that encodes a homologue of the putative YabF protein. The amino acid distribution of YabF and YhaH predict soluble proteins with significant similarity to the NAD(P)H dehydrogenase quinone oxidoreductase, DHQV. To investigate the function of YabF, a strain lacking the yabF-kefC region in E. coli was constructed. The strain was transduced into a kefB background and when transformed with a plasmid expressing only KefC channel activity was greatly reduced. The data suggest that the YabF protein is required in trans for the activity of KefC and preliminary evidence from in vitro-galactosidase fusion studies suggest that yabF and kefC genes may form an operon.

The main objective of this thesis was to develop a substantive theory that explained the phenomenon of detoxification from psychoactive drugs such as alcohol, tranquillisers, opioids, and amphetamines in a medical treatment unit for licit and illicit drug users. The other objectives were to (a) determine if the differences reported in earlier studies between licit and illicit drug users in terms of socio-demographic and drug use variables remain extant, and (b) assess the extent of minor psychiatric morbidity among the participants. Both grounded theory and quantitative methods of data collection and analysis were used in the study.The findings of the quantitative component of the study indicated that there were significant differences between licit and illicit drug users in regard to age, drug use characteristics, and completing the treatment program. That is, illicit drug users were younger than licit drug users, more likely to be poly drug users, and drop out of the program. The prevalence of minor psychiatric morbidity among the participants was 93.6%, and was largely independent of socio-demographic and drug use variables. The high prevalence of minor psychiatric morbidity suggests that the majority of participants warranted further follow-up support in the community after they left the treatment unit. The uptake of referrals for follow-up support, however, was 55.9%.The basic or core social psychological problem identified by the constant comparative method of grounded theory was found to have two parts, both of which were interpreted as forms of disequilibrium. The first part of disequilibrium, which was a precursor to treatment, was conceptualised as Hitting the Wall. The events associated with the symbolic "wall" interrupted the participants' drug focussed lifestyles and induced them to enter treatment. These events and problems were not resolved whilst in ++ / treatment, they lingered with the participants while they were in the unit, and remained to be addressed when they left. Whilst undergoing detoxification the participants encountered the second part of disequilibrium which was categorised as Incompatibility. The problem of Incompatibility was related to the heterogeneity of the participants and the structure of the treatment program that in many cases was unable to accommodate individual differences and needs.The core or basic social psychological process was conceptualised as Seeking Balance through Hanging In. The participants engaged in this process to deal with the disequilibrium of the precursor problem of Hitting the Wall and the problem of Incompatibility encountered in the unit. Seeking Balance through Hanging In was found to have four phases. The phases were Making the Break, Submitting to Cleansing, Fitting In, and Moving On. The process was linear in that the phases were sequential, and failure to complete a phase meant dropping out of the detoxification program. The experience of detoxification was modified by several contextual conditions. These were the physical enviroment, the participants' expectations of withdrawal symptoms, and the workload of the staff.The substantive theory, Seeking Balance through Hanging In, integrated all emergent categories, and explained the experience of the phenomenon of withdrawal from psychoactive drugs in a particular context. Recommendations for further research include testing the described phases and relationships of the substantive theory in similar environments, exploring the importance of the modifying conditions on client outcomes, and undertaking follow-up studies to determine the outcomes of those who completed the program as compared to the outcomes of those who dropped out. In addition, further studies are recommended to assess the transientness of the level ++ / of minor psychiatric morbidity detected among the participants in this study.The findings of this study make an important contribution to understanding the experience of detoxification from the perspective of the participants. The substantive theory has implications for clinical practice, professional education, management, and further research.

This study examined biological mercury removal from soil using mercury-resistant bacteria in soil microcosms. Mercuric chloride was used to artificially contaminate Kidman soil to mercury concentrations of 5 ppm and 10 ppm. Soil moisture content was maintained at three levels, 20%, 30% and 50%. Mercury resistant-bacteria were added to soil samples and the mercury removal rate was compared to control samples without added bacteria. Mercury removal rate was initially enhanced by the addition of bacteria. After 30 days, no difference was observed between samples and controls with initial mercury concentration of 5 ppm when soil moisture content was 20%. At an initial mercury concentration of 10 ppm, soil samples had less mercury remaining than controls after 30 days. Autoclaved soil had a decreased mercury removal rate compared to soil not autoclaved. Addition of nutrient (sucrose) did not increase the mercury removal rate. A slurry-type bioreactor was found to be more efficient than a non-stir type. After 30 days of continuous stirring, 85-90% of the added mercury (10 ppm) was removed, while under the same conditions except no stirring, only around 60% of the mercury was removed. Overall, biological detoxification of mercury from contaminated soil can be achieved by using a slurry-type bioreactor with additon of mercury-resistant bacteria.

Chemical investigation of the transformation of the crucifer phytoalexins brassinin, brassilexin and camalexin by the phytopathogenic fungus <i>Alternaria brassicicola</i> was carried out. The objectives of this study included:<p> 1) the isolation and characterization of the metabolites of biotransformation of brassinin, brassilexin and camalexin by <i>A. brassicicola</i>;<p> 2) determination of the antifungal activity of these phytoalexins and their metabolites against <i>A. brassicicola.</i><p> The phytoalexins were synthesized and characterized using HPLC retention time tR, 1H NMR, 13C NMR, LC-MS and HRMS-ESI data. The metabolites of the biotransformation were also synthesized and characterized similarly. The metabolism of each phytoalexin and their metabolites was studied by analyzing broth extracts by HPLC. The percent inhibition of growth of <i>A. brassicicola</i> was determined by radial growth mycelial assays.<p> The biotransformation of brassinin by <i>A. brassicicola</i> afforded Nb-acetyl-3-indolylmethylamine via indole-3-methylamine intermediate. Brassilexin was metabolized to 3-(amino)methyleneindoline-2-thione by the reduction of the isothiazole ring. Camalexin did not appear to be metabolized or the metabolism was very slow. The results of biotransformation and bioassay studies established that the metabolism of brassinin by <i>A. brassicicola</i> was a detoxification process. However, these studies using brassilexin did not provide a rigorous conclusion. Camalexin showed strong inhibition of growth against <i>A. brassicicola</i> suggesting its importance in defense against this pathogen.