Submitted by Diego Santos (diegosantos@unipampa.edu.br) on 2015-04-10T11:49:39Z No. of bitstreams: 1 111010003.pdf: 1306168 bytes, checksum: 65e96979f53ded7b91f629af13358a87 (MD5) / Made available in DSpace on 2015-04-10T11:49:41Z (GMT). No. of bitstreams: 1 111010003.pdf: 1306168 bytes, checksum: 65e96979f53ded7b91f629af13358a87 (MD5) Previous issue date: 2012-08-20 / O metilmercúrio (MeHg) é um agente tóxico que causa importantes prejuízos à saúde humana e ambiental. Parte desses efeitos está relacionado a sua capacidade de induzir estresse oxidativo. Os mecanismos precisos pelos quais o MeHg leva ao estresse oxidativo ainda não estão bem esclarecidos. Dados na literatura apontam para a participação de selenoproteínas como a glutationa peroxidase e a tioredoxina redutase neste processo. Neste estudo, buscou-se investigar o papel de isoformas de glutationa peroxidase (GPx1 e GPx4) e da tioredoxina redutase (TrxR1) na neurotoxicidade induzida por MeHg em camundongos, focando na atividade e expressão destas proteínas. Nossos resultados mostraram, que o tratamento de camundongos Swiss machos adultos com MeHg (40 mg/L na água de beber) durante 21 dias causa uma diminuição significativa na atividade das enzimas GPx e TrxR no córtex e cerebelo dos animais tratados, em comparação com os controles. Observou-se também uma significativa redução na expressão de GPx1, GPx4 e TrxR1 no cerebelo dos animais tratados, enquanto que no córtex apenas GPx4 e TrxR1 foram afetadas. Concomitantemente a estes resultados, observou-se um aumento significativo na atividade das enzimas antioxidantes SOD, CAT, GR e GST no cerebelo e da CAT no cortex. A expressão de HSP70 foi significativamente aumentada no cerebelo dos animais tratados. Estes dados denotam uma clara resposta celular antioxidante frente aos efeitos tóxicos do MeHg em nosso modelo, reforçando dados da literatura que indicam o estresse oxidativo como um importante mecanismos na neurotoxicidade induzida por este organometal. Além disso, nossos resultados apontam para isoformas de glutationa peroxidase e tioredoxina redutase como importantes alvos moleculares do MeHg e, ao menos, em nosso conhecimento, este é o primeiro estudo demonstrando o papel da GPx4 na neurotoxicidade induzida por este agente tóxico ambiental. Outro objetivo deste trabalho foi investigar os efeitos biológicos do extrato da alga Prasiola crispa(PcE), oriunda do continente Antártico, nos modelos de Drosophila melanogaster e Nauphoeta cinérea. Organismos adaptados a ambientes extremos como a Antártica tendem a apresentarem uma constituição única em termos de metabólitos secundários. Desta forma, estudos que visem à elucidação de efeitos biológicos de organismos oriundos destas regiões tendem a apresentarem relevância do ponto de vista biotecnológico. Nossos dados apontam para um potencial biocida de PcE nos modelos de mosca-da-fruta (Drosophila melanogaster) e barata cinerea (Nauphoeta cinerea), visto que a administração do extrato induziu toxicidade nos dois modelos. A toxicidade em D. melanogaster foi avaliada como percentagem de mortalidade, atividade locomotora (geotaxia negativa) e alterações bioquímicas incluindo atividade acetilcolinesterase (AChE) e marcadores de estresse oxidativo.Também foi investigada a ação cardiotóxica do extrato no modelo de coração semi-isolado de barata cinerea. A administração do extrato(2mg/ml) foi feita por 24 horas e, nas moscas, causou um aumento massivo na mortalidade (aumento de 7,6 vezes em relação ao controle). Também foi observado um aumento significativo na atividade locomotora, indicando uma ação neurotóxica do extrato. A atividade AChE, os níveis de glutationa e formação de hidroperóxido manteve-se inalterada. A atividade da glutationa S-transferase aumentou significativamente após a administração de PcE, já a atividade da catalase diminuiu significativamente em moscas que receberam o extrato. No modelo de coração semi-isolado de barata, foi observado uma diminuição da freqüência cardíaca. A incubação do extrato com DTNB, um forte agente oxidante, bloqueou significativamente o efeito cardiotóxico do extrato, sugerindo que compostos redutores podem ser responsáveis pelo efeito observado. Desta forma, este estudo demonstrou os efeitos tóxicos de PcE, em dois modelos de inseto, sugerindo seu potencial como bioinseticida. Os mecanismos precisos relacionados a este efeito ainda necessitam de esclarecimentos, entretanto, alterações em sistemas antioxidantes vitais podem estar envolvidos. / Methylmercury (MeHg) is a toxic agent that causes severe damage to human health and the environment. These effects are related to its ability to induce oxidative stress. The precise mechanisms by which MeHg leads to oxidative stress are not well understood. Data from literature point to the involvement of selenoproteins such as glutathione peroxidase and thioredoxin reductase in this process. In this study, we sought to investigate the role of isoforms of glutathione peroxidase (GPx4 and GPx1) and thioredoxin reductase (TrxR1) in MeHg-induced neurotoxicity in mice, focusing on activity and expression of these proteins. Our results showed that treatment of adult male mice Swiss with MeHg (40 mg / L in drinking water) for 21 days causes a significant decrease in GPx and TrxR enzyme activity in the cerebral cortex and cerebellum of treated animals when compared to controls. We also observed a significant reduction in the expression of GPx1, GPx4 and TrxR1 in the cerebellum of the treated animals, whereas in the cortex only GPx4 and TrxR1 are affected..In parallel, we observed a significant increase in antioxidant enzymes SOD, CAT, GR and GST in the cerebellum and CAT in cortex. HSP70 expression was significantly increased in the cerebellum of the treated animals. These results show a clear antioxidant cell response against the toxic effects of MeHg in our model, reinforcing the literature data indicating oxidative stress as an important mechanism in the neurotoxicity induced by this organometal. Furthermore, our results point to isoforms of glutathione peroxidase and thioredoxin reductase as important molecular targets of MeHg and, at least, to our knowledge, this is the first study demonstrating the role of GPx4 in the neurotoxicity induced by this toxic environmental agent. Another objective of this study was to investigate the biological effects of the extract of the alga Prasiola crispa (PcE), from the Antarctic continent, in the insect models Drosophila melanogaster and Nauphoeta cinerea. Organisms adapted to extreme environments such as Antarctica tend to present a unique composition in terms of secondary metabolites. Thus, studies aimed at elucidating the biological effects of organisms from these areas tend to be relevant in a biotechnological point of view. Our data demonstrates a potential biocide PcE effect in the fruit fly (Drosophila melanogaster) and lobster cockroach (Nauphoeta cinerea), since the administration of the extract induced toxicity in both models. Toxicity in D. melanogaster was assessed as percentage of mortality, locomotor activity (negative geotaxis) and biochemical measurements including acetylcholinesterase (AChE) and markers of oxidative stress. We also investigated the cardiotoxic action of the extract in a cockroach semi-isolated heart model. The administration of the extract (2 mg / ml) for 24 hours toflies, caused a massive increase in mortality (7.6-fold increase compared to control). We also observed a significant increase in locomotor activity, indicating a neurotoxic action of the extract. AChE activity, glutathione levels and the formation of hydroperoxide remained unchanged. The activity of glutathione S-transferase significantly increased after administration of PcE while catalase activity was significantly decreased in flies that received the extract. A significant decrease in heart rate in the cockroach semi-isolated heart model was observed after PcE administration. The incubation of the extract with DTNB, a strong oxidizing agent, significantly blocked the cardiotoxic effect of the extract, suggesting that reducing compounds may be responsible for the observed effect. Thus, this study demonstrated, for the first time, the toxic effects of PcE, in two insect models, suggesting its potential as a bioinsecticide. The precise mechanisms related to this effect still need clarification, however, changes in vital antioxidant systems may be involved.

Very little is known about why and how the Parkinson's disease (PD) neurodegenerative process begins and progresses. In the course of developments for treatment of PD, the discovery of the inhibition of monoamine oxidase (MAO B) was a conceptual breakthrough, and has now been firmly established. MAO B has also been implicated in the neurodegenerative processes resulting from exposure to xenobiotic amines. For example, MAO B catalyzes the first step of the bioactivation of the parkinsonian inducing pro-neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Additional insight into the mechanism of catalysis of MAO B and the mechanism of neurotoxicity by MPTP is therefore very valuable in the pursuit of the treatment of PD. / Thesis (Ph.D. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2008.

Adolescence is a critical developmental period in which the brain emerges from an immature state to adulthood. This process of brain development is associated to greater cognitive capacity but also to altered emotional behaviour, such as anxiety and depressive symptoms; as well as increased sensation-seeking and risk taking behaviour. The proper development of brain and behaviour into adulthood can be negatively affected by external factors such as drug abuse and environmental conditions. This work consists firstly on, studying the impact of binge ethanol, 3, 4-Methylenedioxymethamphetamine (MDMA) and its combination in adolescent mice. Secondly, study the consequences of early-life stressful experiences (social isolation) into adulthood. Main results obtained from the first objective are that the combination of binge ethanol and MDMA induces emotional-like alterations. These alterations can be prevented by antidepressant treatment. In addition, MDMA induces memory impairments that may be associated to oxidative damage to specific proteins in the hippocampus. Neuroinflammation is also present after MDMA treatment, but not after binge ethanol treatment, in mice striatum. Metabolomic studies indicate that brain metabolism is altered after binge ethanol, MDMA or its combination. Even though these are only preliminary results, these alterations might be due to an imbalance in tryptophan metabolism. Regarding the second objective, our findings indicate that social isolation during adolescence induces an altered response to novel and stressful situations. These alterations are probably due to altered HPA axis activity. / L'adolescència és un període crític en el desenvolupament de l’individu en el qual el cervell va d’un estat immadur a l’edat adulta. Aquest procés va acompanyat d’una elevada capacitat cognitiva però també de freqüents alteracions de tipus emocional, com l’ansietat o els símptomes depressius, així com la cerca de sensacions de risc. Un bon desenvolupament del cervell i del comportament es pot veure negativament afectat per factors externs com són l’abús de drogues i les condicions ambientals desfavorables. Aquest projecte consisteix en primer lloc, a estudiar l'impacte de l’alcohol en excés, la 3, 4-Metilendioximetamfetamina (MDMA) i la seva combinació en ratolins adolescents. En segon lloc, estudiar les conseqüències en l’edat adulta d’experiències estressants durant l’adolescència. Els principals resultats obtinguts referents al primer objectiu són que la combinació d'alcohol en excés i MDMA provoca alteracions de tipus emocional. Aquestes alteracions poden ser previngudes pel tractament amb antidepressius. A més, la MDMA indueix un deteriorament de la memòria que pot estar associada amb el dany oxidatiu a proteïnes específiques de l'hipocamp. També s’ha observat una resposta neuroinflamatòria en el cos estriat dels ratolins després del tractament amb MDMA, però no després del tractament amb etanol en excés. Finalment, estudis de metabolòmica indiquen que el metabolisme cerebral es veu alterat després de l’alcohol en excés, la MDMA o la seva combinació. Tot i que només són resultats preliminars, aquestes alteracions poden ser conseqüència d'un desequilibri en el metabolisme del triptòfan. Referent al segon objectiu, els nostres resultats indiquen que l'aïllament social durant l’adolescència indueix una resposta alterada a situacions novelles i estressants. Aquestes respostes anormals són probablement conseqüència d’alteracions en l’activitat de l’eix HPA.

Many cyanobacteria are reported to produce the nonprotein amino acid β-N-methylamino-L-alanine (BMAA). Cyanobacteria are extensively distributed in terrestrial and aquatic environments and recently BMAA was detected in temperate aquatic ecosystems, e.g. the Baltic Sea. Little is known about developmental effects of the mixed glutamate receptor agonist BMAA. Brain development requires an optimal level of glutamate receptor activity as the glutamatergic system modulates many vital neurodevelopmental processes. The aim of this thesis was to investigate the developmental neurotoxicity of BMAA, and its interaction with the pigment melanin. Autoradiography was utilized to determine the tissue distribution of 3H-labelled BMAA in experimental animals. Behavioral studies and histological techniques were used to study short and long-term changes in the brain following neonatal exposure to BMAA. Long-term changes in protein expression in the brain was also investigated using matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS). A notable targeting of 3H-BMAA to discrete brain regions e.g. hippocampus and striatum in mouse fetuses and neonates was determined by autoradiography. BMAA treatment of neonatal rats on postnatal days 9–10 induced acute but transient ataxia and hyperactivity. Postnatal exposure to BMAA also gave rise to reduced spatial learning and memory abilities in adulthood. Neonatal rat pups treated with BMAA at 600 mg/kg showed early neuronal cell death in the hippocampus, retrosplenial and cingulate cortices. In adulthood the CA1 region of the hippocampus displayed neuronal loss and astrogliosis. Lower doses of BMAA (50 and 200 mg/kg) caused impairments in learning and memory function without any acute or long-term morphological changes in the brain. The MALDI IMS studies, however, revealed changes in protein expression in the hippocampus and striatum suggesting more subtle effects on neurodevelopmental processes. The studies also showed that BMAA was bound and incorporated in melanin and neuromelanin, suggesting that pigmented tissues such as in the substantia nigra and eye may be sequestering BMAA. In conclusion, the findings in this thesis show that BMAA is a developmental neurotoxin in rodents. The risks posed by BMAA as a potential human neurotoxin merits further consideration, particularly if the proposed biomagnifications in the food chain are confirmed.

The neurotoxic potential of intravenous administered benzylpenicillin (BPC) was studied in rabbits with intact blood-CNS barriers and rabbits with experimental E. coli meningitis. At onset of epileptogenic EEG activity or seizures, serum, CSF and brain tissue were collected for assay of BPC. Based on the fact that, in tissues, BPC seems to remain extracellularly, brain concentrations of BPC were expressed as brain tissue fluid (BTF) levels, calculated as lOx the concentration in whole brain tissue. Neurotoxicity could be precipitated in all rabbits. In normal rabbits BTF levels of BPC were considerably higher than those in CSF indicating a better penetration across the blood-brain barrier (BBB). BPC penetrated better to CSF and BTF in meningitic rabbits than in normal controls, suggesting some degree of damage of the BBB concomitant with meningeal inflammation. E. coli meningitis did not increase the neurotoxicity of BPC. In control rabbits the intracistemal injection of saline resulted in some degree of pleocytosis. Unmanipulated animals are therefore preferable as controls. Epileptogenic EEG-changes was the most precise of the two variables used for demonstration of neurotoxicity. EEG-changes were therefore used as neurotoxicity criterion in the following rabbit experiments. To evaluate the effect of uraemia alone and uraemia plus meningitis on the neurotoxity of BPC in rabbits, cephaloridine was used to induce uraemia. Meningitis was induced by intracistemal inoculation of a cephalosporinresistant strain of E. cloacae. Untreated  rabbits were used as controls. Uraemia resulted in increased BTF penetration of BPC, possibly explained by permeability changes in the BBB and/or decreased binding of BPC to albumin. Uraemia did not result in increased penetration of BPC into the CSF of non-meningitic rabbits. Uraemic non-meningitic rabbits had the highest BTF levels of BPC at the criterion, indicating that cephaloridine-induced renal failure increased the epileptogenic threshold in these rabbits. The combination of uraemia and meningitis increased the neurotoxicity of BPC since the criterion was reached at considerably lower BTF levels of BPC. Meningitis, either alone or together with uraemia, did not increase the neurotoxicity in comparison to control rabbits. Higher BTF levels of BPC were found in meningitic rabbits than in controls with intact blood-CNS barriers at onset of EEG-changes. In all groups of rabbits there was a pronounced variability of BPC levels in the CSF while the intra-group variations in BTF levels were much smaller. Thus, BTF and not CSF levels were decisive for the neurotoxicity of BPC. Using   the same EEG-model, the neurotoxic potential of imipenem/cilastatin (I) and a new penem derivative, FCE 22101 were compared in a cross-over study. Both I and FCE 22101 were significantly more neurotoxic than BPC. While BTF levels of the three antibiotics could be detected in all tested rabbits, detectable CSF levels were only found in one of twelve rabbits treated with I or FCE 22101, indicating that BTF concentrations rather than CSF ones are decisive for neurotoxicity of ß-lactam antibiotics. The EEG-model used was found to be a suitable model for cross-over studies of intravenously administered antibiotics. Using the "silent-second" as EEG-threshold, a CNS interaction between intraperitoneally administered BPC and intravenous thiopental was demonstrated in rats. The most probably site for this interaction is the organic acid transport system out of the CNS. Thiopental distribution in the rat brain seemed to depend not only on its lipid solubility. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1988, härtill 5 uppsatser.</p> / digitalisering@umu

Very little is known about why and how the Parkinson's disease (PD) neurodegenerative process begins and progresses. In the course of developments for treatment of PD, the discovery of the inhibition of monoamine oxidase (MAO B) was a conceptual breakthrough, and has now been firmly established. MAO B has also been implicated in the neurodegenerative processes resulting from exposure to xenobiotic amines. For example, MAO B catalyzes the first step of the bioactivation of the parkinsonian inducing pro-neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Additional insight into the mechanism of catalysis of MAO B and the mechanism of neurotoxicity by MPTP is therefore very valuable in the pursuit of the treatment of PD. / Thesis (Ph.D. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2008.

Very little is known about why and how the Parkinson's disease (PD) neurodegenerative process begins and progresses. In the course of developments for treatment of PD, the discovery of the inhibition of monoamine oxidase (MAO B) was a conceptual breakthrough, and has now been firmly established. MAO B has also been implicated in the neurodegenerative processes resulting from exposure to xenobiotic amines. For example, MAO B catalyzes the first step of the bioactivation of the parkinsonian inducing pro-neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Additional insight into the mechanism of catalysis of MAO B and the mechanism of neurotoxicity by MPTP is therefore very valuable in the pursuit of the treatment of PD. / Thesis (Ph.D. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2008.

The developing brain goes through a number of developmental periods during which it displays an increased sensitivity to exogenous disturbances. On such period is the so called “Brain growth spurt” (BGS) which in humans takes place starting from the third trimester of pregnancy and throughout the first few years of life. The corresponding period in rats and mice is the first postnatal weeks. Exposure to relatively modest concentrations of the brominated flame retardant PBDE-99 during the second week of life in mice causes a more or less permanent impairment in the ability of the animals to adjust properly to environmental changes at adulthood. This “late response on early exposure” reflects the long-term consequences of disrupting the developing brain during a sensitive time period. The cellular mechanisms underlying the behavioral effects are far from clear. To address the initial damage occurring around the time of exposure, the approach used in this thesis is to use proteomics to analyze the effects of PBDE-99 on protein expression soon (24 hours) after exposure of the neonatal mouse on postnatal day (PND) 10.The thesis comprises the effects on the proteome in three distinct brain parts: cerebral cortex, striatum and the hippocampus. In addition, an in vitro model was developed and used to evaluate the PBDE-99 effects on cultured cerebral cortex cells from embryonic rat brains. Gel-based proteomics (2D-DIGE) coupled to MALDI- or ESI-MS has been used throughout for the proteomics experiments, but other techniques aimed at analyzing both proteins and mRNA have also been used to better characterize the effects. Even if the protein complements expressed by the different brain parts and separated with 2D-DIGE are seemingly similar, the effects are apparently specific for the different brain regions. In hippocampus, PBDE induces effects on proteins involved in metabolism and energy production, while the effects in striatum point towards effects on neuroplasticity. PBDE-99 changes the expression of cytoskeletal proteins in the cerebral cortex 24 hours after exposure. Interestingly, in vitro exposure of cerebral cortex cells to a PBDE-99 concentration in the same order of magnitude as in the in vivo neonatal brain also induces cytoskeletal effects, in the absence of cytotoxicity. This may suggest effects on regulatory aspects of cytoskeletal dynamics such as those involved in neurite sprouting. This thesis also addresses the problems involved in presenting proteomics data. Many of the available methods and approaches for presenting transcriptomics data are not suitable for isoform rich protein data. Modifications of existing methods and the development of a new approach (DEPPS) is also presented. Most importantly, the thesis presents the application and usefulness of proteomics as hypothesis generating techniques in neurotoxicology.

Aflatoxins are produced by Aspergillus flavus fungi, mainly A. parasiticus and A. nomius. Aflatoxin B1 (AFB1) is the most common and highly toxic mycotoxin, presents carcinogenic, mutagenic and teratogenic effects. This mycotoxin has been detected in cultures of worldwide importance such as maize, groundnuts, beans, rice, wheat, cotton, sorghum, fruit and also in animal feed. AFB1 exerts its effects after its conversion into liver 8,9-epoxide by the action of cytochrome P-450, which reacts with cellular macromolecules, including proteins, RNA and DNA. Furthermore, there is an increase in levels of reactive oxygen species, altered neurobehavioral performance, damage to motor coordination, and decreased protein levels. Studies show that AFB1 alter the levels of neurotransmitters such as norepinephrine, serotonin and dopamine, and it is known that these changes influence the behavior of animals, also inhibits the activity of the enzyme Na+, K+-ATPase. This enzyme in the brain is essential for the maintenance of the electrochemical gradient, maintenance of resting potential and the release and uptake of neurotransmitters. Thus, a decrease in activity Na+, K+-ATPase could cause increased neuronal excitability, facilitating the occurrence of seizures. Thus, the aim of this study was to investigate the influence of AFB1 in facilitating seizures induced by a subconvulsant dose of pentylenetetrazol (PTZ), and evaluate its toxic effects on the brain, by determining the activity of Na+, K+-ATPase and oxidative stress parameters after acute exposure to AFB1 in rats. EEG recording of the animals was performed after acute oral administration of AFB1 (250 mg/kg) followed by a subconvulsant dose of pentylenetetrazol (30 mg/kg, ip). Prior administration of AFB1 to PTZ reduced the latency of myoclonus, did not alter the total amplitude of the brain waves, and concomitant exposure to PTZ reduced the activity total, α1 and α2/α3 of the enzyme Na+, K+-ATPase in the cerebral cortex. In the hippocampus, the AFB1 and PTZ reduced total and α2/α3 activity of the Na+, K+-ATPase. The AFB1 not alter the activity of catalase (CAT), and glutathione-S-transferase (GST) in the cerebral cortex of animals. We conclude that AFB1 exerts neurotoxic effect, facilitating seizures induced by PTZ possibly by inhibiting Na+, K+-ATPase activity. / As aflatoxinas são produzidas principalmente pelos fungos Aspergillus flavus, A. parasiticus e A. nomius. A aflatoxina B1 (AFB1) é a micotoxina mais frequente e altamente tóxica, apresenta efeitos carcinogênicos, mutagênicos e teratogênicos. Esta micotoxina tem sido detectada em culturas de importância em todo o mundo, como milho, amendoim, feijão, arroz, trigo, algodão, sorgo, frutas e também em rações de animais. A AFB1 exerce seus efeitos após sua conversão hepática em 8,9-epóxido, pela ação de enzimas do citocromo P-450, o qual reage com macromoléculas celulares, incluindo proteínas, RNA e DNA. Além disso, há um aumento nos níveis de espécies reativas de oxigênio, alteração do desempenho neurocomportamental, prejuízos à coordenação motora, e diminuição dos níveis proteicos. Estudos revelam que a AFB1 altera os níveis de neurotransmissores como a norepinefrina, serotonina e dopamina, e sabe-se que estas alterações influenciam no comportamento dos animais, como também inibe a atividade da enzima Na+,K+-ATPase, enzima que no cérebro, é essencial para a manutenção do gradiente eletroquímico, manutenção dos potenciais de repouso e liberação e captação de neurotransmissores. Assim, uma diminuição da atividade Na+,K+-ATPase pode ocasionar aumento da excitabilidade neuronal, facilitando a ocorrência de convulsões. Sendo assim, o objetivo deste trabalho foi investigar a influência da AFB1 em facilitar as convulsões induzidas por uma dose subconvulsivante de pentilenotetrazol (PTZ), e avaliar seus efeitos tóxicos sobre o cérebro, através da determinação da atividade da Na+,K+-ATPase e parâmetros de estresse oxidativo após a exposição aguda à AFB1 em ratos. Foi realizado o registro eletroencefalográfico dos animais após a administração oral aguda de AFB1 (250 μg/kg) seguida por uma dose subconvulsivante de pentilenotetrazol (30 mg/kg, i.p.). A administração prévia da AFB1 ao PTZ reduziu a latência das mioclonias, não alterou a amplitude global das ondas cerebrais, e a exposição concomitante ao PTZ reduziu a atividade total, α1 e α2/α3 da enzima Na+,K+-ATPase no córtex cerebral. No hipocampo, a AFB1 e o PTZ reduziram a atividade total e α2/α3 da Na+,K+-ATPase. A AFB1 não alterou a atividade da catalase (CAT) e da glutationa-S-transferase (GST) no córtex cerebral dos animais. Concluímos que a AFB1 exerce efeito neurotóxico, facilitando as convulsões induzidas por PTZ, possivelmente devido à redução da atividade da enzima Na+,K+-ATPase.

Astrócitos são células gliais com fundamental importância no sistema nervoso central (SNC), tanto em condições fisiológicas quanto patológicas. Estas células são essenciais na plasticidade neural, no metabolismo de neurotransmissores, na defesa antioxidante, na regulação do metabolismo energético, na homeostase iônica, na resposta inflamatória, na manutenção da barreira sangue-cérebro, na migração neuronal e na estabilização da comunicação entre as células. Assim, alterações em funções astrocitárias (como as que ocorrem no envelhecimento) estão relacionadas a importantes alterações na funcionalidade cerebral. Desta forma, esta tese teve por objetivo demonstrar que a cultura de astrócitos derivada de ratos Wistar adultos, desenvolvida e caracterizada pelo nosso grupo de pesquisa, pode ser um modelo de estudo fidedigno e versátil das propriedades celulares astrocitárias. Nossos resultados apontam que esta metodologia pode ser utilizada para elucidar o perfil de aminoácidos e gliotransmissores assim como da atividade enzimática glial e gerenciamento de neurotransmissores. Também demonstramos que a cultura adulta não é derivada de progenitores neurais e que parâmetros mitocondriais observados no cérebro adulto foram reproduzidos in vitro. A análise de respostas a estímulos demonstrou ser variável, dependendo da idade dos animais. Da mesma forma, o uso de culturas de diferentes idades revelou o efeito antienvelhecimento da guanosina, sugerindo sua atividade glioprotetora. Finalmente, demonstramos que culturas preparadas a partir de animais neonatos submetidas a um modelo de senescência in vitro apresentam respostas diferentes das apresentadas por culturas preparadas a partir de animais adultos e/ou envelhecidos, demonstrando que o modelo mais adequado para elucidar propriedades astrocitárias do cérebro maduro é o derivado de animais adultos. Portanto, demonstramos com este estudo a importância da disponibilidade de uma ferramenta como a cultura de astrócitos adultos e elucidamos características bioquímicas, celulares e moleculares desta ferramenta, evidenciando algumas de suas diferenças em comparação à cultura preparada a partir de ratos neonatos. Assim, ampliamos a compreensão das propriedades e funções celulares desta ferramenta, fornecendo respostas mais aproximadas às respostas fornecidas por astrócitos do cérebro maduro in vivo, especialmente no estudo do envelhecimento e das doenças neurodegenerativas. / Astrocytes are glial cells of pivotal importance in the central nervous system (CNS), both in physiological and pathological conditions. Some of their roles include neural plasticity, neurotransmitter metabolism, antioxidant defenses, control of energy metabolism, ionic homeostasis, inflammatory response, formation and maintenance of blood-brain barrier, neuronal migration and cellular communication. Thus, changes in astrocytic function (such as occurs in aging) are related to changes in brain function. The aim of this thesis was to demonstrate that astrocyte cultures from adult Wistar rats (developed and characterized by our research group) might be a reliable and versatile tool for studying astrocytic cellular properties. Our results suggest that this culture model is suitable to study the amino acids content and gliotransmitters, as well as glial enzymatic activity and neurotransmitter management. Next, we showed that the astrocyte cultures are not derived from neural progenitors and tissue mitochondrial parameters were reproduced in in vitro cultures. Responses to stimulus were variable, depending on the animals’ age. Accordingly, guanosine presented an anti-aging effect, indicating its glioprotective activity. Finally, we showed that cultures prepared from newborn rats submitted to an in vitro senescence model presented different responses when compared with mature animals, indicating that our culture model is the most suitable model to represent astrocytic properties in the mature brain. Therefore, this study demonstrates the relevance of this tool to understanding the biochemical, cellular and molecular properties of adult astrocytes, showing some differences related to the culture prepared from newborn animals. Thus, we amplify the comprehension about cellular functions of this tool, providing closer responses related to mature brain in vivo, especially regarding studies about aging and neurodegenerative diseases.