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An In Vitro Comparison Study of Two Cell Therapies for Cardiac Repair
No full textCardiovascular disease continues to be the leading cause of death in New Zealand and throughout the world. Apart from orthotopic heart transplantation, no current treatment can prevent the progression of disease. Due to long waiting lists, heart transplantation is not a viable option for most patients. As a result, cell-therapies have garnered attention due to their potential to replace lost cardiac cells, repairing and regenerating the damaged myocardium. Despite recent advances in regenerative medicine, one of the biggest challenges remaining in translating cell-based therapies to the clinic is determining the best cell type to use.
Many different cell types have been investigated for their potential in cardiac repair. Cardiac progenitor cells (CPCs) and adipose derived stromal cells (ASCs) both show potential to promote cardiac repair. CPCs have been shown to greatly promote cardiac repair while ASCs increase angiogenesis and can be isolated in greater numbers through a relatively easy procedure. Despite advantages and disadvantages being known for various cell types, few studies exist directly comparing different cell types for cardiac repair. As both ASCs and CPCs have regenerative potential, this study aimed to directly compare these cells for in vitro cardiac repair.
ASCs and CPCs were successfully isolated from epicardial adipose tissue (EAT) and right atrial appendage (RAA) samples from the same patients through explant culture. Flow cytometry analysis showed the ASC population to be heterogeneous for mesenchymal cell marker CD90 and positive for CD29, CD73 and CD105 while CPCs were negative for the circulating haematopoietic cell marker CD34, positive for CD105 and heterogeneous for CD90. ASCs and CPCs showed comparable CD90 expression and combined CD90/CD105 expression, but CPCs showed significantly higher CD105 expression.
A wound healing assay over 24 hours to determine the migration potential of the cells showed CPCs to have significantly higher wound coverage at 6-, 12- and 18-hour time points compared to ASCs. However, after the 24-hour period, the wound coverage was comparable between both cell types. This showed both cells were able to migrate to the site of injury, but CPCs were able to do so faster.
ASCs and CPCs were then cultured in serum deprived hypoxia (1% O2) to mimic ischaemic conditions. Normoxic conditions (20% O2) were used as a control. Proliferation was measured and no significant difference was observed between ASC and CPC proliferation in normoxia and hypoxia. Gene expression of HIF1A, AKT1, FGF2 and PDGFA were measured to assess the cell responses to ischaemic conditions. No significant difference was found between either cell type or oxygen condition for any mRNA expression.
To compare the paracrine effects of ASCs and CPCs, conditioned media (CM) was collected following serum deprived normoxic and hypoxic culture. IGF-1 and VEGF-A concentrations were measured. IGF-1 concentration was significantly higher in both normoxic and hypoxic ASC CM compared to CPC CM. VEGF-A concentration was comparable across all groups. AC16 cardiomyocytes cultured in hypoxia and treated with CPC CM had significantly lower levels of apoptosis compared to ASC CM. CPC normoxia CM was also able to significantly increase HIF1- protein expression in AC16 cardiomyocytes cultured in hypoxia. However, CM-treated HUVECs showed no significant change in angiogenesis between each group or compared to the untreated control.
In conclusion, several differences were found between CPCs and ASCs with CPCs having a marginal improvement in therapeutic effects compared to ASCs for cardiac repair. Hence, this study has provided evidence that there could be a difference between using these two cell types as therapy for cardiovascular disease. However, further in vitro and in vivo studies are required to adequately determine which cell type is more appropriate for cardiac repair
Chemistry of a Stable Vitamin C Glycoside in Apples (Malus spp.) and Other Fruit Crops
No full textThe primary aim of the research described in this thesis was to investigate an ascorbyl glycoside tentatively identified in crab apples (Malus sylvestris) by a non-targeted metabolomics study (unpublished thesis, J. Cho, 2016). The interest in this metabolite arose from the possibility that it may be involved in the translocation of ascorbate from leaf to fruit in apples. This hypothesis was based on its similarities to tutin-glycosides and sucrose-glycosides which are utilised for long distance translocation in Coriaria and Cucurbita spp. respectively. The chemotaxonomy of the Coriaria genus was also investigated as part of this research (Appendix 2).
Isolation of the target ascorbyl glycoside from crab apples was achieved via acetylation of the crude extract and subsequent purification. This compound was definitively characterised by comparison to a synthetic standard and found to be 2-O-β-D-glucopyranosyl-L-ascorbic acid (AA2βGlc). This derivative was found to have greater stability than ascorbate and was comparable to AA2αGlc, which is commonly used in cosmetic products as stabilised pro-vitamin C. This was only the third reported occurrence of an ascorbyl glycoside in plants, and the second report of this specific metabolite.
Quantitative HILIC LC-MS was used to analyse leaf and fruit tissue of five apple genotypes at three separate collection dates representing the start, middle and end of fruit development. Crab apples were found to have an extremely high concentration of AA2βGlc in their fruit (>500 mg/100 g FW), but only trace quantities (<10 mg/100 g FW) were detected in fruit of domestic cultivars (Braeburn and Royal Gala). Leaves of all varieties contained AA2βGlc at similar concentrations (approx. 30 mg/100 g FW). A significant increase in AA2βGlc concentration was observed between the start and middle of fruit development (October-December). Collection and analysis of fruit and leaf material from an additional 12 fruit crops, predominantly of the Rosaceae family, revealed that they also contained AA2βGlc in their leaves. While previously thought to be rare, these results extend the known occurrence of this metabolite to 14 species and five families.
Based on the distribution in leaves and fruit it was proposed that AA2βGlc was utilised as a stabilised form of ascorbate for translocation between leaves and fruit. In order to provide evidence for this hypothesis phloem exudates of five apple genotypes were analysed by HILIC LC-MS. AA2βGlc was present in phloem of all genotypes, but ascorbate was found at greater concentrations, which showed that AA2βGlc was not the major form of translocated ascorbate. Glucosidase assays were used to determine if enzyme activity indicative of phloem unloading, i.e. hydrolysis of AA2βGlc to ascorbate, was present in any of the five apple genotypes. Protein extracts of stems and leaves were found to have generic β-glucosidase activity, but none of the tissue types tested showed activity towards AA2βGlc. Further work is required to understand the biological role of this metabolite in apples.
The synthesis of four ascorbyl glycosides was achieved, establishing the structure of the naturally occurring metabolite and providing a valuable resource to the experiments described above. Previously unreported routes to access AA2βGlc and AA2βGal, as well as methodology towards AA5βGlc and AA6βGlc, are described. Inconsistencies in the reported NMR data for ascorbyl glycosides were clarified by demonstrating that these spectra were highly pH dependent.
This work dramatically enhances what is known regarding ascorbyl glycosides in plants and provides a foundation from which to determine the physiological role of this previously overlooked metabolite. Further work should focus on more rigorous biological experiments to determine whether the accumulation of AA2βGlc in crab apples is a result of translocation from leaves or in situ biosynthesis. This may lead to the development of cultivars with increased vitamin C concentrations, consequently adding both nutritional and commercial value to one of New Zealand’s largest horticultural exports
Understanding the ‘Pink’ vote in Aotearoa
No full textThere is little written on how gay men engage in the electoral process, and this lack of data extends to New Zealand. When speaking to peers about this topic, it was the widely held view that gay men support the Labour Party, as there has been a historic level of support for the queer community from the Labour Party. This study takes a mixed method approach to answer the dual research questions: which political parties do gay men in New Zealand vote for, and why do they vote for those parties? By using data from the New Zealand Values and Attitudes Survey, and the New Zealand Election Survey, this thesis shows a broad picture of how gay men vote. Interviews in Auckland, Wellington, and Dunedin are used to expand on this, and to understand why gay men in New Zealand vote, and why they vote the way they do. Three theories of voting predictions are used to analyse this data: proximity theory, social structure theory, and rational choice theory. The results of the interviews and data analysis shows that, despite the assumption that gay men support the Labour Party, the majority of gay men in New Zealand vote for a diverse range of left-wing parties, and vote for parties that most closely align with their own values. Gay men were also driven to vote out of a sense of civic duty. Despite a small sample size, this thesis is a first-step in filling an academic gap in the electoral participation of queer people
The antiviral mechanism and viral antagonism of host histone deacetylase 4 in influenza A virus infection
No full textInfluenza virus continues to be an important global pathogen which poses serious health and economic challenges. Influenza virus causes regular seasonal epidemics, intermittent and unpredictable pandemics and deadly zoonotic outbreaks. The currently available antiviral strategies used against influenza are limited in their effectiveness. The rapid evolution of influenza viruses has precluded the development of a universal vaccine and has meant that the annually administered vaccine is only variably effective. Furthermore, the two classes of antiviral drugs used against influenza have only limited effectiveness due to rise in drug resistance. Therefore, there is a pressing need to develop a greater understanding of the virus-host interactions that are critical for influenza virus multiplication and pathogenesis. Such understanding would aid in the development of more effective and long lasting anti-influenza virus strategies.
This PhD investigates the role of host histone deacetylase HDAC4, in influenza A virus (IAV) infection, the most significant genus of influenza. Histone deacetylases (HDACs) are a family of enzymes that catalyse the deacetylation of acetylated histone and non-histone proteins. Previously, it has been shown that HDAC1, HDAC2, HDAC6 and HDAC11 all possess anti-influenza virus properties. HDAC1, HDAC2 and HDAC11 are involved in promoting the innate immune response during influenza infection. HDAC6 restricts influenza virus release by deacetylating α-tubulin and decreases viral replication by degrading the viral polymerase and enhancing the RIG-I innate immune response. Currently, no studies have investigated the role of HDAC4 in IAV infection. Given the similarity between different HDAC members, we hypothesised that HDAC4 also plays a role in inhibiting IAV replication. Hence, we investigated the effects of HDAC4 depletion and overexpression on IAV replication using primarily human lung epithelial cells and IAV PR/8/34(H1N1) strain as a model.
The outcomes of this project reveal that depletion of HDAC4 enhances the replication of influenza virus by up to 4-fold. Conversely, influenza virus replication was inhibited by up to 49% in cells overexpressing HDAC4, indicating an antiviral role for HDAC4. Mechanistically, HDAC4 was found to be involved in the influenza virus-induced host innate antiviral response. Specifically, we observed decreased phosphorylation of STAT1 in HDAC4 depleted cells, which corresponded to decreased levels of the interferon effector genes (IFITM3, ISG15 and viperin). Conversely, HDAC4 overexpressing cells enhanced STAT1 phosphorylation, resulting in greater expression of the downstream interferon effector genes. We also found that influenza virus actively targets HDAC4 to downregulate its expression both at mRNA and polypeptide levels, likely as a means to inhibit its antiviral function. The HDAC4 mRNA is degraded by the IAV endonuclease PA-X while HDAC4 polypeptide is cleaved by IAV-induced host caspase 3.
In summary, the outcomes of this PhD implicate HDAC4 as an anti-influenza host factor that is a component of host innate antiviral response. In addition, it is revealed that influenza virus strongly antagonises HDAC4 to subvert its antiviral activity. Thus, the data presented here contributes to our molecular understanding of host HDACs-influenza virus interplay and strengthening the notion that HDACs are a family of anti-influenza host factors
Factors driving life-histories in brown trout Salmo trutta exhibiting partial migration behaviours
No full textThe behaviors of some partially migratory salmonids, at both the among- and within-species levels, can be established early - on during their respective lives. For those species that have a plastic early life history in these regards, a variety of biological and environmental factors can result in some juvenile fish in a population to either stay resident within their natal streams or become migratory. This study examines the role of intraspecific competition as a trigger, either to remain resident or emigrate, for YoY (young-of-the-year) non-native (introduced) brown trout Salmo trutta found in a number of populations of selected natal streams in a large catchment in South Island, New Zealand. Brown trout are known to have the genetically-mediated flexibility leading to the potential establishment of a variety of within-population alternatives for migratory life-history outcomes (e.g., stay put, move out of the immediate area, become anadromous). The role of positive feedback loops generated by parents that either stay to live out their whole lives within their natal stream, or leave either to go to other freshwater environments (other streams, lakes) or the ocean, before spawning and producing viable offspring is examined in this study.
This thesis provides strong evidence for the role of competition in initiating downstream movement of YoY brown trout populations. These are mechanisms leading to the establishment of feedback loops between the migratory or resident life-histories of adults and the density of juvenile fish while they are stream rearing. Competition amongst juveniles was assessed by estimating and comparing the demands for energy and space of a number of rearing populations of YoY fish and the capacity of study stream to provide food and space. Stream-carrying capacity was estimated using data on fish-habitat suitability, invertebrate drift, energetic demand and the trophic selectivity of YoY trout.
In the lowland reaches of my study catchment the population densities of YoY fish in their natal streams were generally high. I found the intensity of competition within this category of natal streams, amongst the high-density populations of the offspring of migratory trout, to also be high. Anadromy was the dominant life-history strategy for adult brown trout in these low-gradient, lowland streams. Along the lowland reaches, positive associations between YoY loss rate (driven by both emigration and mortality) and intra-cohort competition, were observed. The intensity of competition amongst YoY cohorts was primarily determined by temperature-mediated energy restrictions rather than territorial limitations. In contrast, in the headwater streams which are inhabited by resident trout, the abundance of YoY juvenile fish was relatively low, and there was no evidence to indicate that competition influenced the loss rate of these fish. Hence, based on the densities, competition and self-thinning of YoY brown trout, this suggests that the majority of the recruitment across the catchment was driven by the high reproductive inputs into lowland spawning grounds from adults with migratory life-history traits. However, an analysis of the recruitment sources of fish using otolith microchemistry indicated that a high proportion of adults reproducing in the coastal part of the catchment originated from the upland part of the catchment. This indicates that populations of anadromous and potamodromous brown trout are likely comprised of individuals originated from throughout the entire catchment. Most notably, the geomorphology of the landscape limits the upstream migration and spawning distribution of large fecund migratory trout due to physical barriers.
These results highlight the genetically-mediated life-history flexibility of brown trout and their ability to shift between either migratory or resident phenotypes at early life stages. This flexibility is sustained even in populations that have originated from a likely-narrow genetic pool of introduced lineages of brown trout. Considering current changes in global-climates, the findings of temperature-driven energetic restrictions on species distributions may be highly important for brown trout management and conservation in New Zealand and elsewhere. The observed flexibility in life-history traits and high straying from natal streams contributes to their ability to utilize a wide range of opportunities across catchments
Contronymic secularism: The constitutional politics of religion in Fiji
No full textIn 2012, Fiji’s military regime declared secularism as an official policy for Fiji’s new constitution, and the key to securing inter-religious tolerance and an inclusive public space for Indigenous (iTaukei) Fijian Christians and Indo-Fijian Hindus and Muslims. However, instead of reconciling Fiji’s politics of religion, debates on secularism polarised public discourse, provoked Christian state secessionist movements, and entrenched the power of the state. Drawing on detailed analysis of the 7,000 public submissions to Fiji’s 2012 Constitution Commission, previous drafting consultations, past constitutions, judicial decisions, parliamentary debates and interview data with thirty-one senior political and religious leaders, this doctoral thesis argues that a significant factor for this failure lies with the term ‘secularism’ itself. The broad semantic range of this anglophone term in Fiji’s constitutional discourse – stretching from inter-religious fairness under God to a godless, worldly materialism – along with its polemical use by political actors, obstructed Fiji’s potential for political compromise.
This thesis contends that in Fiji secularism persists as a contronym, as it denotes two distinct and contrary referents. Fijians debating secularism do not advance competing arguments about the same topic, but raise different topics using the same word. Instead of disagreement and dialogue, therefore, Fiji’s contronymic secularism has produced misunderstandings: a double monologue, whereby disputing parties speak past each other, deepening animosity and misplacing consensus. For example, the bitter conflict between Indigenous Christian Fijians rejecting a secular state (as godless, worldly materialism) and liberals, the military and Indo-Fijians demanding one (as inter-religious fairness), disguised the fact that both sides largely supported the religion/state arrangements already written into the 1997 Constitution.
The thesis shows that this contronymic missing of meaning continues, principally, because it is expedient for partisan actors on either side of Fiji’s divided politics not to make common meaning. Five case-studies of religion/state controversies that occurred after 2012 are analysed to demonstrate the ways in which Fijians – in government, in opposition, in religious offices, in court and in open rebellion to the state – either deliberately or intuitively, employ a contronymic secularism to subvert the voice of their political opponents. Ultimately, this rhetorical practice returns power to the incumbent ruling authority (the state), which, with dialogue undermined, can resort to alternative, coercive means to govern. In summary, the top-down introduction of the term ‘secularism’ into Fiji’s public discourse reproduced, reified and entrenched the very problems that the notion of secularism ostensibly seeks to redres
Therapeutic Jurisprudence in Aotearoa New Zealand's Family Justice System
No full textAotearoa New Zealand’s Family Justice System (“FJS”) has a dual therapeutic and judicial mandate. The balancing of the two roles has created difficulty since the Family Court’s inception in 1981. The FJS has been reviewed four times, and each review has considered how the dual roles should be balanced. The most recent review was completed in mid-2019. There have been concerns that the FJS is not meeting its therapeutic mandate. While some of the concerns with the FJS are related to changes made in 2014, some of the concerns have persisted for decades.
Therapeutic Jurisprudence (“TJ”), the study of the psychological impact of the law, can be used as a lens for professionals to see the law through its psychological impact. Its four areas of inquiry are the law, legal rules, legal procedures and legal roles (legal professionals in the justice system). Many of the concerns in the FJS are about professionals and the use of TJ to improve legal roles is an important change that can be brought to improve the FJS. Changes to laws and procedures takes time, but changes to roles can happen immediately. Furthermore, even if rules and procedures are antitherapeutic, legal professionals can improve the therapeutic impact of the FJS in the way they go about their work.
This thesis sets out the background and development of TJ. It then compares TJ to the other ‘vectors’ of the comprehensive law movement. It analyses how TJ has had an impact in family law before discussing the history of the FJS, the current state of the FJS, and analysing the proposed changes to the FJS released this year through a therapeutic lens. There is then a discussion about issues relating to the FJS independent of the 2014 reforms. Finally, there is a case study and discussion that highlight professionals adopting TJ can have an important, positive impact on those involved in the FJS.
While the FJS was formed with a dual therapeutic and judicial mandate, the FJS is not meeting its therapeutic mandate in many ways. The 2014 reforms to the FJS have been largely negative and have had a largely anti-therapeutic effect. The recommendations following the 2018-2019 review of the FJS are largely consistent with TJ and give several helpful recommendations to improve the therapeutic impact of legal roles. However, the recommendations do not go far enough to ensure that the proposed changes are fully resourced and enforceable
Chemical and microbial determinants of N2O emission from denitrification in pasture soils
No full textNitrous oxide (N2O) is a potent greenhouse gas and ozone depleter accounting for 6.2% of globally emitted CO2 equivalents. Denitrification, the microbial reduction of NO3->NO2->NO->N2O->N2, is a significant source of N2O in agricultural soils. The end product of the process (N2O or N2) is determined by the net balance of N2O production and consumption steps which are in turn sensitive to soil conditions. Therefore, mitigation of N2O emission from denitrification is dependent on our basic understanding of factors regulating the production and consumption of this gas. Here, I present results contrasting the potential biological and chemical causes of varied N2O emission potential in 20 New Zealand pastures soils.
Soil N2O/N2O+N2 was determined by gas chromatography of anoxic soil incubations amended with NH4NO3 and compared correlatively to potential chemical or biological controls or directly through chemical amendments to soil incubations. Investigations revealed soil N2O/N2O+N2 was largely determined by the timing of N2O reduction: some soils concurrently produced and reduced N2O from the start of incubations, while others delayed N2O reduction until almost all added N was accumulated as N2O in incubation vial headspace. The later pattern is hypothesized to result in high N2O emissions in situ. Differential nitrite (NO2-) accumulation between alternative phenotype soils and responses to exogenous NO2- suggest high NO2- accumulation could account for delayed N2O reduction activity. However, the impact of carbon additions (Concurrent -> Sequential) and successive nitrate additions (Sequential -> Concurrent) suggest carbon availability and delayed N2O reductase synthesis could also be important driving factors. NO accumulation and inhibition is proposed as a potential proximal mechanism linking alternate drivers of soil denitrification phenotypes.
In addition, correlations between changes in microbial community composition as measured by 16S rRNA gene sequencing and denitrification phenotypes suggest a potential distal cause for delayed N2O reduction activity but also highlight an ongoing issue with denitrification research: our inability to satisfactorily identify whether the correlations between soil microbial community composition and N2O emission potential reflect a true causative relationship. To address this, I utilized a soil extracted cell based experimental design to answer a fundamental question about denitrification in complex soil communities: Does microbial community composition really matter for a N2O emission outcome and if so, how much compared to chemical controls? Incubations of various combinations of soil extracted cells and water extractable chemical compoenents (e.g. carbon, pH) from contrasting high N2O/N2O+N2 and low N2O/N2O+N2 ratio soils suggested microbial community origin did indeed impact N2O/N2O+N2 ratio but impacts were smaller than that of extractable chemical components. In the absence of pH effects, predictable impacts of cell origin imply some generalizations can be made about what is a low N2O emitting community; low N2O/N2O+N2 soil cells or chemistry typically lowered incubation N2O/N2O+N2 and high N2O/N2O+N2 soil cells or chemistry vice versa. Serendipitously, these cell based incubations also provided evidence that low carbon availability can induce increased N2O emissions.
Together, these investigations build evidence for a combined role of soil chemistry and microbial community composition as determinants of soil N2O emissions, support the increasing focus on microbial community composition in denitrification research and imply both soil chemistry and microbial community composition must be considered in prediction and management of soil N2O emissions in the future
Normative foreign policy - the Kiwi way. To what extent has New Zealand been acting as norm entrepreneur in the areas of nuclear free policy and promoting free trade?
No full textNorms are standards of appropriate behaviour for actors and as such they do have a role in international politics. When norms are adopted by actors, they affect the actors’ policy behaviour, and consequently, the actors’ practices. Changing norms and policy practices of the actors in the system would result in changing the intersubjective knowledge of the actors and eventually the system. In international politics, small states are more inclined to international law and norms than great powers. Although realists and structuralists argue that small states need to behave according to great powers’ interests and small states are system-ineffectual, these arguments hold only to military power. In terms of economic power, small states have control over their success, while the power over opinion is not related to the size of the actors. Therefore, small states can influence global politics by intellectual leadership, norm-setting and norm entrepreneurship.
The thesis observes whether and to what extent New Zealand has been acting as norm entrepreneur in the policy areas of nuclear-free politics and promoting free trade. To regard an actor as norm entrepreneur in a policy area, the actor should have no authority over the addressees of the proposed norm, the actor should consider the norm as appropriate for others too, the extent and intensity of the conscious efforts to promote the norm internationally should be sufficient, the norm-promoting efforts should be performed during the emerging and cascade phases of the norm life-cycle, and the actor should behave consistently with the norm. According to these criteria, New Zealand has been a norm entrepreneur in nuclear-free policy since 1984. Concerning free-trade, New Zealand has also been a norm entrepreneur between 1984 and 2017. Both cases illustrate how small states can influence international politics. Based on the findings, small states’ domestic policies may have larger effects on world politics than their direct international advocacy, other states can ignore the advocacy and remain reluctant to modify their policy agendas
The Pesticide Loss via Volatilisation (PLOVO) Model and an Environmental Fate Study of Chlorpyrifos
No full textPesticides are an important tool in modern crop management to ensure high quality and high yield food production. However, pesticide Volatilisation from agricultural fields can have a significant impact on non target, sensitive ecosystems, and can result in a loss of revenue for farmers. I further developed and validated the Pesticide Loss via Volatilisation (PLOVO) model. The model is based on multiphase partitioning, that describes pesticide Volatilisation loss from a planted agricultural field and predicts 24-hour cumulative percentage Volatilisation (CPV24h) losses. The model allows the user to adjust the chemical-physical properties of the pesticide, species-specific plant surface chemistry, plant size, soil type, and climatic conditions. An average equation for the plant-air partition coefficient (Kplant-air) was found and implemented in the model to describe the plant-surface chemistry interactions with pesticides. The model was used to address questions about how the volatilisation of pesticides from plants and soil contribute to the total volatilisation from a field, and how plant species and growth stage affect the amount of pesticide lost to the atmosphere. Results are displayed on chemical space diagrams for sets of hypothetical Kplant-air, soil-air (Ksoil-air) and water-air (Kwater-air) partition coefficient combinations under different environmental conditions and plant species and growth stage. We found that the CPV24h increased with increasing temperature, foliar intercept fraction and wind speed, and with decreasing plant size. Pesticides tended to volatilise more from plants than soil. CPV24h was highly varied between plant growth stage but was less varied between plant species. Our model is therefore a promising new screening assessment tool for pesticide Volatilisation from a planted agricultural field.
Chlorpyrifos is a chlorinated organophosphorus pesticide that has caused concern over recent years due to its widespread global use and its non-specific toxicity. Chlorpyrifos is used as an insecticide to protect a wide variety of crops. Its mode of action targets the nervous system of an organism by inhibiting the enzyme acetylcholinesterase (AChE). Studies have shown that low environmental doses of chlorpyrifos can cause detrimental effects on non-target organisms such as honey bees. In order to understand the risk of chlorpyrifos exposure posed to non-target organisms, we first must understand the fate of the insecticide in the environment. Thus, I conducted a field study where chlorpyrifos was applied to an agricultural field planted with Phacelia tanacetifolia. The concentration of chlorpyrifos was then monitored in soil and Phacelia leaves over the course of three weeks. The concentration of chlorpyrifos was greater in leaves than soil, and chlorpyrifos was lost (whether through volatilisation, degradation or another loss pathway) more rapidly from leaves than soil. The chlorpyrifos field study was also used to further test and validate the PLOVO model. I compared the predicted chlorpyrifos concentrations generated by the model to the measured chlorpyrifos concentrations from the field. I found that the model-generated concentrations did not agree with the measured concentrations in either soil or leaves. This is not to say that the model does not accurately predict the volatilisation of pesticides from a planted field in the first 24 hours, rather more information would be needed to extend the model to predict the total loss of a pesticide from leaves and soil over a longer time period. In order to extract chlorpyrifos from leaves and soils, I developed and optimised two selective pressurised liquid extraction (SPLE) methods. I utilised the fat absorbing properties of Florisil and the pigment absorbing properties of graphitised carbon black (GCB) to produce clean extracts for GC/MS analysis. The recovery of chlorpyrifos from soil and leaves was 92% and 79%, respectively. While these methods were optimised for the extraction of chlorpyrifos from soil and leaf matrices, it has the potential to be extended as a multi-residue method