Thesis (Ph. D.)--University OF MICHIGAN. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University OF MICHIGAN. / Also issued in print.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

It was found that there was a specific interaction between peptidolipid C18H35O (Stearoyl)-Phe-Trp-Ser-His-Glu and paraoxon. The aromatic residue groups were involved in the recognition between paraoxon and the peptidolipid, because the fluorescence of Trp in the peptidolipid at 351 nm was quenched by paraoxon in the subphase. When paraoxon was dissolved in the subphase, the surface potential-area (delta V-A) isotherm for the peptidolipid A displayed an unusual shape. This was interpreted on the basis of Infrared Reflection-Absorption Spectroscopy (IRRAS) results as being due to the reorientation of the benzene ring of paraoxon, which changed from parallel to the air-water interface in the absence of a monolayer to a tilted orientation upon interacting with the peptidolipid Langmuir monolayer. The secondary structure of oganophosphorus acid anhydrolase (OPAA) Langmuir monolayer in the absence and presence of diisopropylfluorophosphate (DFP) in the subphase was also studied by the IRRAS and Polarization Modulated-IRRAS (PM-IRRAS). The shape of OPAA molecules is supposed to be elliptic and the long axis of OPAA was parallel to the air-water interface in the absence of DFP in the subphase, whereas the long axis became perpendicular in the presence of DFP. This result explains the decrease of the limiting molecular area of OPAA Langmuir monolayer when DFP was dissolved in the subphase. Using the Langmuir monolayer technique, the surface properties of aequorin were studied. The results showed that aequorin formed a stable Langmuir monolayer and the surface pressure-area isotherms were dependent on both pH and ionic strength. At a pH higher or lower than 7.6, the limiting molecular area decreased. The addition of calcium chloride to the Tris/HCl buffer subphase (pH 7.6) caused an increase of the limiting molecular area of the aequorin Langmuir monolayer. The fluorescence spectra of a Langmuir-Blodgett (LB) monolayer of aequorin in the presence of calcium chloride indicated that the aequorin transformed to the apoaequorin. The Langmuir monolayer of aequorin and apoaequorin was studied by IRRAS and PM-IRRAS techniques. The different behavior of aequorin and apoaequorin at the air-water interface was explained by the fact that aequorin formed dimers at air-water interface but apoaequorin was monomer. It was more difficult for a dimer to be tilted by the compression of the Langmuir monolayer.

No description available.

Les agents chimiques de guerre et leurs dérivés pesticides sont des molécules toxiques qui provoquent une incapacité temporaire ou des dommages permanents allant jusqu’à la mort de l’individu. Une des voies majeures de la contamination est la pénétration cutanée. La protection de la peau semble donc importante pour prévenir de ces dangers. Cette thèse concerne l’élaboration de nouveaux topiques protecteurs cutanés contenant des polymères HASE fluorés greffés avec des nanoparticules de silice, cérine ou titane. Dans un premier temps les actifs ont été synthétisés en grosse quantité et leurs propriétés de mouillabilité améliorées. Les tests toxicologiques ont montré que les actifs n’étaient pas irritants pour la peau et non toxiques pour l’environnement. La formulation de ces polymères a permis le développement de deux nouvelles crèmes barrières contre la pénétration du paraoxon dont l’efficacité est dépendante de la présence des nanoparticules. Le greffage des nanoparticules à un polymère HASE fluoré et leur formulation a donc permis le développement de nouveaux topiques efficaces. L’évaluation de l’efficacité a été réalisée sur membranes artificielles et confirmée sur explants de peaux humaines. Enfin, le peu de disponibilité des explants de peaux humaines a motivé le développement d’un modèle d’efficacité utilisant des épidermes humains reconstruits. / Chemical warfare agents and pesticides are toxic molecules causing temporary incapacitation or permanent harms leading to the death of people. One of the major routes of contamination is the percutaneous penetration. Skin protection is important to prevent these dangers. The aim of this thesis is to develop new active topical skin protectants based on nanoparticular networks containing fluorinated HASE polymers grafting with silica, cerium or titanium nanoparticles. First, polymers were synthesized in larger quantity and their wettability properties improved. Toxicological studies have showed that these compounds are non-irritant and non-toxic for the environment. The formulation of these polymers has led to the elaboration of two new barrier creams against paraoxon penetration whose efficiency is dependent on the presence of nanoparticles. Therefore, the grafting of nanoparticles to fluorinated HASE polymer and their formulation have enabled the development of new active topical skin protectant. Efficiency evaluation was done using artificial membranes and was confirmed on ex vivo human skin. The limited availability of human skin explants has motivated the development of a new efficiency model using reconstructed human epidermis.

<p>This thesis examined neurotoxic effects of nicotine exposure during a defined critical period of neonatal brain development in mice.</p><p>In our environment there are numerous hazardous contaminants that an individual can be exposed to during its entire lifetime. In many mammalian species the neonatal period is characterised by a rapid development of the brain. The present studies have identified a defined critical period during the neonatal brain development in mice, where exposure to low doses of nicotine causes permanent disturbances in the cholinergic nicotinic receptors and altered behaviour response to nicotine at adult age. This adult reaction to nicotine, a hypoactive response, was the opposite of that observed in control animals and animals exposed to nicotine before or after this period. Animals showing a hypoactive response to nicotine lacked nicotinic low affinity binding sites in the cerebral cortex. Furthermore, neonatal exposure to nicotine affected learning and memory in adult animals, an effect that was time-dependent. This thesis also showed that neonatal exposure to nicotine increased adult susceptibility to a repeated exposure of nicotine, manifested as an even more pronounced effect in spontaneous behaviour after challenging doses of nicotine. In these animals the nicotinic receptors in the cerebral cortex, assayed by a-bungarotoxin, was decreased. </p><p>Neonatal exposure to nicotine was also shown to increase adult susceptibility to the organophosphate paraoxon, a known cholinergic agent, and to the brominated flame retardant 2,2´,4,4´,5-pentabromodiphenyl ether, a novel environmental agent, at adult age. This was seen at doses that did not affect behaviour in control animals, and was manifested as deranged spontaneous behaviour and reduced habituation, aberrations that also worsened with age. </p><p>The results indicate that differences in adult susceptibility to environmental pollutants are not necessarily an inherited condition. Rather they may well be acquired by low dose exposure to toxic agents during early life.</p>

This thesis examined neurotoxic effects of nicotine exposure during a defined critical period of neonatal brain development in mice. In our environment there are numerous hazardous contaminants that an individual can be exposed to during its entire lifetime. In many mammalian species the neonatal period is characterised by a rapid development of the brain. The present studies have identified a defined critical period during the neonatal brain development in mice, where exposure to low doses of nicotine causes permanent disturbances in the cholinergic nicotinic receptors and altered behaviour response to nicotine at adult age. This adult reaction to nicotine, a hypoactive response, was the opposite of that observed in control animals and animals exposed to nicotine before or after this period. Animals showing a hypoactive response to nicotine lacked nicotinic low affinity binding sites in the cerebral cortex. Furthermore, neonatal exposure to nicotine affected learning and memory in adult animals, an effect that was time-dependent. This thesis also showed that neonatal exposure to nicotine increased adult susceptibility to a repeated exposure of nicotine, manifested as an even more pronounced effect in spontaneous behaviour after challenging doses of nicotine. In these animals the nicotinic receptors in the cerebral cortex, assayed by a-bungarotoxin, was decreased. Neonatal exposure to nicotine was also shown to increase adult susceptibility to the organophosphate paraoxon, a known cholinergic agent, and to the brominated flame retardant 2,2´,4,4´,5-pentabromodiphenyl ether, a novel environmental agent, at adult age. This was seen at doses that did not affect behaviour in control animals, and was manifested as deranged spontaneous behaviour and reduced habituation, aberrations that also worsened with age. The results indicate that differences in adult susceptibility to environmental pollutants are not necessarily an inherited condition. Rather they may well be acquired by low dose exposure to toxic agents during early life.

Organophosphates are insecticides which result in acute adverse signs when exposed at toxic doses by animals and lead to death if left untreated. The current treatment for organophosphate toxicity includes atropine and the federally approved oxime 2-PAM. However, 2-PAM is not very effective at crossing the blood brain barrier which results in prolonged inactivation of acetylcholinesterase, which is the primary target of organophosphates, in the brain even after administration. The novel oximes, Oxime 15 and Oxime 20, are able to cross the blood brain barrier and reactivate the inhibited acetylcholinesterase. In this experiment with six animal species frequently used in toxicity studies, they were proven to be just as effective and sometimes better than 2-PAM at reactivating acetylcholinesterase or butyrylcholinesterase inhibited by paraoxon, chlorpyrifos-oxon, phorate-oxon, or dicrotophos. The detoxication enzymes butyrylcholinesterase, carboxylesterase, and paraoxonase were also studied as potential influences of the toxicity of the organophosphates in these different species.

Os praguicidas organofosforados (OPs) são amplamente utilizados na indústria química e na agricultura em todo o mundo. Muitos deles são potenciais causadores da \"Neuropatia Retardada Induzida por Organofosforados\" (NRIOP), caracterizada pela degeneração distal de axônios do sistema nervoso central e periférico (degeneração do tipo Walleriana). O praguicida triclorfom (dimetil 2,2,2-tricloro-1-hidroxietil fosfonato) tem sido utilizado em larga escala na produção agrícola e também no controle de vetores transmissores de várias doenças. Há relatos de efeitos neuropáticos em seres humanos expostos ao triclorfom, mas apesar disso, o seu potencial neuropático e seus mecanismos de neurotoxicidade ainda não foram elucidados. Assim, no presente estudo foram avaliados os mecanismos de toxicidade do praguicida OP triclorfom utilizando linhagem SH-SY5Y de neuroblastoma humano como modelo, e também foram avaliados possíveis agentes neuroprotetores em células tratadas com o bem estabelecido indutor da neuropatia mipafox. Foram utilizados como possíveis neuroprotetores: a amilorida e nimodipino (bloqueadores de canais de cálcio tipo T e L respectivamente), MDL 28170 (inibidor (III) de calpaína) e liraglutida (um agonista do \"glucagon like peptide\" -GLP-1). Foram usados o mipafox, como modelo de indução da NRIOP e o paraoxon, como modelo não indutor da NRIOP. Os ensaios de inibição e reativação da esterase susceptível à neuropatia (ESNp) e de citotoxicidade mostraram que somente o mipafox e o triclorfom apresentaram inibição e envelhecimento da ESNp superiores a 70% em concentrações com baixa toxicidade, condição compatível com a indução da NRIOP. A ativação das calpaínas foi observada apenas no tratamento com mipafox, efeito este inibido pela nimodipina, amilorida e pelo MDL 28170. Triclorfom e o mipafox causaram elevação significativa nos níveis de cálcio intracelular e da caspase-3, além de inibir significativamente o crescimento de neuritos. Os três OPs avaliados foram capazes de diminuir a captação da glicose, que foi aumentada nos grupos tratados com mipafox associado com neuroprotetores. As quatro substâncias utilizadas como possíveis neuroprotetoras reduziram significativamente o dano causado pelo mipafox sobre os neuritos. O modelo usado no estudo mostrou-se apropriado para a caracterização dos OP neuropáticos, pois permitiu a diferenciação dos efeitos do mipafox (neuropático) e do paraoxon (não-neuropático). Os dados obtidos indicam que o triclorfom tem potencial indutor de NRIOP, e a amilorida, nimodipino liraglutida e MDL apresentaram potencial neuroprotetor / Organophosphorus (OP) pesticides are widely used in the chemical industry and agriculture around the world. \"Organophosphate Induced Delayed Neuropathy\" (OPIDN) is characterized by distal degeneration of axons of the central and peripheral nervous system (Wallerian-type degeneration). The OP trichlorfom (dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate) has been used in large scale in agricultural production and also for the control of vectors that are transmitter of diseases. There are reports of neuropathic effects in humans exposed to trichlorfon, but despite this, its neuropathic potential and mechanisms of neurotoxicity have not yet been elucidated. Thus, in the present study we evaluated the mechanisms of toxicity of trichlorfom and possible neuroprotective agents in SH-SY5Y human neuroblastoma cells treated with the well-established neuropathy inducer mipafox. The following neuroprotective agents were used: amyloride and nimodipine (T and L-type calcium channel blockers, respectively), MDL 28170 (calpain inhibitor (III) and liraglutide (a \"glucagon-like peptide\" - GLP-1 agonist). Mipafox was used as neuropathic OP and paraoxon was used as a non-neuropathic OP. Inhibition and reactivation assays of neurpathy target esterase (NTE) and cytotoxicity showed that only mipafox and trichlorfon showed inhibition and aging of 70% of the NTE in concentrations that presented low toxicity, consistent with development of OPIDN. Activation of calpain was observed only in the treatment with mipafox, an effect inhibited by nimodipine, amyloride and MDL 28170. Triclorfom and mipafox caused significant increase in the levels of intracellular calcium, caspase-3 and significantly inhibiting neurite growth. All three OPs assessed in this work caused a decrease in glucose uptake, which was increased in groups treated whith mipafox plus neuroprotectors. Substances used as possible neuroprotective agents significantly reduced the inhibitory effect of mipafox on neurite outgrowth. The model used in the study proved to be appropriate for characterizing neuropathic OPs, because it allowed a differentiation of the effects of mipafox (neuropathic) and paraoxon (non-neuropathic). The data obtained indicate that trichlorfonm has potential in cause OPIDN. Amiloride, nimodipine, MDL and liraglutide have presented potential neuroprotective effects