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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Exposures and health effects among field workers using the organophosphate chlorpyrifos /

Cattani, Marcus P. S. January 2004 (has links)
Thesis (Ph.D.)--Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Includes article published in Annals of Occupational Hygiene, 2001, v. 45 (4), p. 299-308. Bibliography: leaves 267-278.
2

The role of the endocannabinoid system in immune homeostasis with an emphasis on the immune effects of carboxylesterase inhibition by chlorpyrifos in murine lung tissue

Szafran, Brittany Nichole 30 April 2021 (has links)
The endocannabinoid system is composed of endocannabinoids (eCBs), their cognate receptors, and their biosynthetic and catabolic enzymes. Inhibition of serine hydrolases (catabolic enzymes), such as carboxylesterases (CES), might result in the accumulation of eCBs. eCBs, such as 2-arachidonoylglycerol (2-AG), have been shown to increase or reduce inflammation via engagement with cannabinoid receptors on immune cells. This research focuses on exploring the ability of eCBs and their metabolizing enzymes to regulate inflammation. First, a negative feedback mechanism between inflammation and the eCB system was examined by identifying serine hydrolases inhibited by lipopolysaccharide (LPS) stimulation in mice. Ces2g activity was inhibited and Il6 levels were induced in the murine spleen, suggesting a role for this enzyme in an inflammatory response, possibly to limit inflammation. IL-6 did not influence 2-AG hydrolytic activity in human peripheral blood mononuclear cells (PBMCs), but monocytic MAGL was shown to be the predominant 2-AG hydrolytic enzyme in these cells. To investigate a separate mechanism by which serine hydrolases and eCBs may regulate immune responses, mice were treated with chlorpyrifos (CPF), a pesticide known to inhibit serine hydrolases, at doses that do not inhibit acetylcholinesterase in the nervous system. This research is focused on lung tissue since epidemiologic studies have linked pesticide exposures to respiratory diseases. At low doses, Ces1c (adult and neonatal mice) and Ces1d (neonatal mice) were markedly inhibited by CPF (2.5 mg/kg, 7 d, PO). Stimulation with LPS (1.25 mg/kg, IP) following the final CPF dose produced minimal differences in lung immune responses to LPS. In follow up experiments utilizing wild-type and Ces1d-/- mice, a downregulation of Ces1c mRNA in adult Ces1d-/- mice corresponded to an upregulation of Tnfa mRNA in response to LPS in CPF-treated mice. Additionally, Ces1d was found to be expressed in murine alveolar macrophages, suggesting these cells could be used to study the role of CES1 in immunity. Overall, Ces enzymes appear to play a role in immune homeostasis either through a protective mechanism or a negative feedback mechanism to control inflammation.
3

Effects of Chlorpyrifos-oxon on Prohormone Convertase Enzyme Activity

Harshman, Sean William 17 June 2009 (has links)
No description available.
4

Détermination des paramètres de la cinétique du chlorpyrifos

Gougeon, Andréanne January 2004 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
5

Thyroid development in larval lake sturgeon (Acipenser fulvescens) and the potential thyroid disruption associated with exposure to the organophosphate pesticide chlorpyrifos

Burnett, Duncan 23 April 2014 (has links)
The thyroid hormone system plays a major role in larval development, growth, and metabolism in fish. Therefore, any anthropogenic alteration in thyroid function could have dramatic effects on individual fitness. In this study Lake Sturgeon, Acipenser fulvescens, larvae were exposed to a commercially used organophosphate pesticide, chlorpyrifos (0, 5, 500 and 2000ng/L), from hatch until the onset of exogenous feeding (~12 days at 14C). The presence of thyroid follicles was first observed at 6 days post hatch (dph). Molecular expression of thyroid receptor α (TRα) increased from 3 to 12dph and then decreased from 12 to 21dph. TRα expression was also significantly higher in brain, liver and muscle at 67dph when compared to TRβ. Of the circulating hormones only free-T3 was consistently measured in larval homogenates from all development time-points sampled. Exposure to chlorpyrifos had no effect on growth or thyroid follicle morphology during the course of the experiment.
6

Dissipation and Leachability of Formulated Chlorpyrifos and Atrazine in Organically-amended Soils

Xiao, Yunxiang III 10 December 1997 (has links)
Bioremediation was studied in soils containing high concentrations of formulated chlorpyrifos (5 mg kg-1 Dursban® 4E) and atrazine (5 mg kg-1 AAtrex® 4L) using amendments including lignocellulosic sorbents, microbial nutrients (vegetable oil, corn meal and fertilizers), and microbial extracts from organic media previously exposed to these pesticides (chlorpyrifos and atrazine, respectively). Radiolabeled atrazine was used to examine the various dissipation routes in contaminated soil, also amended with lignocellulosic sorbents and microbial nutrients. Both chlorpyrifos and atrazine dissipation from contaminated soils was enhanced by organic-based material amendments. The half-lives of chlorpyrifos based on extractability for soils unamended and amended with vegetable oil and peat moss were 87 and 52 days, respectively. The half-lives of atrazine in unamended and amended soil (vegetable oil, peat moss and fertilizers) were 175 and 40 days, respectively. The leachability of chlorpyrifos from contaminated soil was dramatically reduced by 82% during the first 30 days of incubation in treatments amended with vegetable oil and peat moss while only a 28% of reduction in leachability occurred in the corresponding unamended controls. Only a slight reduction of atrazine leachability was detected in amended treatments after 120 days of incubation. Differences were found in the leachability of chlorpyrifos and atrazine when they were applied to soil either as technical grade or formulated material. The presence of surfactants and other adjuvants in formulated chlorpyrifos (Dursban® 4E) reduced chlorpyrifos leachability in contaminated soil. Chlorpyrifos leachability was reduced by 43% in the formulated chlorpyrifos treatments, whereas there was a negligible decrease in technical chlorpyrifos treated soil during the first 3 days after contamination. Atrazine extractability and leachability was not affected by its formulation (AAtrex® 4L). Amendments with lignocellulosic sorbents and nutrients decreased atrazine®s volatility from contaminated soils. After 16 weeks of incubation, less than 1% of 14C-atrazine was volatilized from incubated soils. Overall, after 16 weeks of incubation less than 4% of 14C-atrazine was mineralized and more radioactivity was recovered from amended treatments than unamended treatments as 14CO2. The major portion of radioactivity (62%) was associated with physisorbed atrazine represented by the ethylacetate extract I from unamended treatments while only 28% of initial applied radioactivity was recovered in the corresponding amended treatments. Based on the sum of radioactivity in humic and fulvic acids, approximately 14% of radioactivity was incorporated or chemisorbed atrazine and its metabolites in both unamended and amended treatments. Forty-five percent of the initially applied radioactivity was associated with alkali insoluble fraction in amended treatments but only 17% of the initially applied radioactivity was detected in the corresponding unamended treatments. Less than 2 % of initial activity associated with physisorbed portions of fulvic acids and alkaline insoluble fraction indicated as the radioactivity in methylene chloride and ethylacetate extract II . Over time, more radioactivity was associated with polar atrazine hydroxylated degradation products. / Ph. D.
7

A solid phase microextraction/gas chromatography method for estimating the concentrations of chlorpyrifos, endosulphan-alpha, edosulphan-beta and endosulphan sulphate in water /

Adam, Hassan Ali. January 1900 (has links)
Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2003. / Word processed copy. Summary in English. Includes bibliographical references (leaves 93-96). Also available online.
8

Synthetic and Natural Environmental Compounds as Potential Facilitators of Mptp-Induced Parkinsonism

Dodd, Celia Anne 20 April 2009 (has links)
Parkinson's disease (PD) is a neurodegenerative Lewy body disorder characterized by severe motor deficits, followed by cognitive dysfunction with progression of the disease. Environmental exposure has been suggested as a possible contributor to the development of PD and this view is linked to the discovery of the nigrostriatal neurotoxin MPTP. MPTP can induce dopamine specific degeneration within the basal ganglia often resulting in motor deficits similar to PD. MPTP used in the C57BL/6 mouse is a widely used animal model of PD. The pyrethroid permethrin (PM), and the organophosphate chlorpyrifos (CPF), can produce changes in dopaminergic nigrostriatal neurons, the primary target of PD and MPTP-induced neurotoxicity. Such insecticide induced changes in the basal ganglia could exacerbate the onset or severity of PD. Chronic exposure to the metal manganese (Mn) can damage the globus pallidus (GP) of the BG, and produce motor deficits similar to PD. Since the GP is part of the BG circuitry essential for motor control, and is synaptically integrated with the nigrostriatal pathway, Mn may exacerbate MPTP-induced neurotoxicity. Because the BG is disynaptically linked to the mesocortical pathway, a dopaminergic pathway that is important for cognition, Mn induced damage in the BG could indirectly affect the mesocortical pathway as well. This study investigated the pesticides, permethrin and chlorpyrifos, and the heavy metal, manganese as possible environmental compounds that could exacerbate PD in the MPTP treated C57BL/6 mouse. The first part of this dissertation used immunohistochemistry to examine insecticide induced effets on MPTP-induced neurotoxicity in the dorsolateral striatum of the C57BL/6 mouse, the principal target of the nigrostriatal pathway. Tyrosine hydroxylase (TH) was used as a marker for loss of dopaminergic neuropil and glial fibrillary acidic protein (GFAP) was used as a marker of glial activation in the striatum. Three experiments assessed effects of 1) PM (200 mg/kg), 2) CPF (50 mg/kg) & 3) PM + CPF, on MPTP (30 mg/kg) neurotoxicity. Immunohistochemistry revealed a decrease in TH staining and an increase in GFAP staining with MPTP (30 mg/kg). A main effect increase in GFAP was observed for PM (200 mg/kg), but not for CPF (50 mg/kg) or PM+CPF. Insecticides, alone or combined, did not alter MPTP-induced toxicity. . However, the absence of the PM-induced increase in GFAP staining following combined insecticide treatment suggests a neuroprotective effect. The next set of experiments in this dissertation looked at the effect of Mn on MPTP-induced neurotoxicity in the nigrostriatal and mesocortical dopaminergic pathways of the C57BL/6 mouse. Inductively Coupled Plasma atomic emission spectrometry revealed striatal Mn levels were significantly increased with multiple dose 100, 50, and 25 mg/kg MnCl2. Administration of Mn (MnCl2 s.c., Days 1, 4, & 7) in the MPTP (20 mg/kg i.p., Day 8) treated C57BL/6 mouse revealed Mn and MPTP interactions for locomotor activity, grip strength, and repeated measures of learning. Mn attenuated the effect of MPTP on striatal DOPAC, and facilitated the effect of MPTP on cortical DA and DOPAC. Mn also attenuated the MPTP induced decrease in cortical DAT. While these data support the notion that insecticides can produce tissue damage in the nigrostriatal pathway, in this case, these insecticide induced changes were not found to be strong enough to facilitate PD-like tissue damage. While Mn did not always facilitate MPTP neurotoxicity in the mesocortical and nigrostriatal dopaminergic pathways, these results demonstrate Mn and MPTP can interact in a complex way to alter dopaminergic function as well as motor and cognitive behavior. Differences in brain uptake mechanisms and metabolism of Mn and MPTP, could explain why combined administration of Mn and MPTP differentially affect dopaminergic activity in the nigrostriatal and mesocortical pathways. / Ph. D.
9

Changes in the Murine Nigrostriatal Pathway Following Pyrethroid and Organophosphate Insecticide Exposure: An Immunohistochemical Study

Pittman, Julian Thomas 01 October 2002 (has links)
Parkinson's disease (PD) is a debilitating motor disorder that primarily afflicts older individuals (> 50yrs). Although its cause is unknown, many factors are thought to contribute to the disease. There is growing epidemiological evidence supporting a link between pesticide exposure and PD. The present immunohistochemical study was undertaken to characterize the role of insecticide exposure in the etiology of idiopathic PD. The insecticides selected for study were the pyrethroid permethrin (PE) and the organophosphate chlorpyrifos (CP), both of which possess properties that could damage or disrupt the nigrostriatal pathway, which is the principal neurodegenerative target in PD. The present study examined possible alteration of the amount of dopamine re-uptake transporter protein (DAT), within the striatum of the C57BL/6 mouse, using DAT antibodies, following low (0.8, 1.5 & 3.0 mg/kg) and high (200 mg/kg) doses of PE, respectively. Possible nigrostriatal terminal degeneration was examined using antibodies to tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine synthesis, following treatment with 50 mg/kg of CP alone or in combination with the high dose of PE. For both the high dose of PE alone and for the combined PE/CP treatment, glial fibrillary acidic protein (GFAP) antibodies were used to examine the possibility of non-degenerative tissue injury. Groups of matched treated/vehicle-control mice received three IP injections of the insecticide/dose of interest over a 2-week period. Counts of immunoreactive (IR) neuropil in the dorsolateral striatum were made from four pre-selected fields per striatal tissue section. Counts were compared between matched sections, processed on the same slide, from a treated mouse and its vehicle control. A mean difference score, across slides, for each treated/vehicle control pair was determined. All low dose PE groups showed a trend of decreased DAT IR neuropil, but only the 3.0mg/kg group showed a statistically significant reduction (p<.0078). The 200 mg/kg PE group showed a trend toward reduced TH IR neuropil that was not statistically significant, but a significant increase in GFAP IR (p = .048) was observed. No significant change in TH IR neuropil was observed for CP (50mg/kg) alone. A significant increase was observed for GFAP IR neuropil for the PE/CP (200/50 mg/kg) combination dose (p = .033). The combined insecticide treatment failed, however, to produce a significant change in TH IR within the striatum, compared to vehicle controls. These data suggest that the significant increases in GFAP IR neuropil, in the striatum, reflect some form of tissue insult, following exposure to a high dose of PE, or PE/CP in combination, that is insufficient to induce degeneration of dopaminergic terminals within the temporal interval investigated. Although such damage may be sufficient to account for previously reported decreases in maximal dopamine uptake observed with high doses of these compounds, the DAT IR data appear to indicate that this damage is unlikely to be a change in the amount of DAT in these high dose conditions. The decreases in striatal DAT IR neuropil observed for low doses of PE suggest an alteration in the normal integrity of the nigrostriatal pathway and in the route by which environmental toxins may enter dopaminergic neurons. / Master of Science
10

Charaterization of Chlorpyrifos Toxicity on the Pancreatic Beta Cell Line RINm5f

Yan, Zhongyu 18 November 2010 (has links)
No description available.

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