Synaptosomal membrane functions were monitored, after in vitro exposure to select environmental pollutants, in synaptosomal preparations originating from rat cerebral cortices. The uptake of NE and 5HT into the synaptosomes was monitored as was the K+-dependent phosphate activity of the membrane. CH3HgCl, Hg(NO3)2, CdCl2, diisopropylfluorophosphate (DFP), paraoxon, acrylamide and Kepone were the test chemicals whose effects were studied. CH3HgCl, Hg(NO3)2 and Kepone had the greatest inhibitory effects on NE and 5HT uptake. The concentrations producing 50 percent inhibition (IC50) were 1.4x10-4, 4.0x10-4, and 9.4x10-5 M, respectively, for NE uptake while the IC50's for 5HT uptake were 1.9x10-4, 6.0x10-4, and 3.3x10-4 M, respectively. Maximal inhibition was 60-100 percent at 10-3 M while the effective concentration range was between 10-4-10-3 M. The remaining test compounds produced no significant inhibition at concentrations up to 10-3 M. K+-dependent phosphatase was strongly inhibited by CH3HgCl, Hg(NO3)2, CdCl2, and Kepone with IC50's of 1.5x10-6, 0.032x10-6, 1.5x10-6, and 13.0x10-6 M, respectively. The effective inhibitory concentrations for these chemicals ranged from 10-7-10-3 M and suggested a specific high affinity inhibition. DFP, paraoxon and acrylamide did not produce a significant inhibition at concentrations between 10-5-10-3 M. A correlation of the phosphatase and monoamide uptake inhibitions, in search of a cause-effect relationship, was not suggested from the data. However, the low affinity inhibition (IC50 greater than 10-5 M) of the NE and 5HT uptake by CH3HgCl, Hg(NO3)2 and Kepone, along with the general shape of the dose-response curve is suggestive of an all-or-none inhibition. The apparent high affinity inhibition (IC50 less than 10-5 M) of the phosphatase demonstrates the specific influences of these compounds can have on enzymatic processes. Such enzymatic inhibition could be of critical importance if these neurotoxicants were able to penetrate the synaptosomal or even neuronal membrane and gain access to the metabolic and synthetic machinery.

This study examined the effect of neurotoxic chemical exposures on brain processes using Single Photon Emission Computed Tomography (SPECT). A control group carefully screened for good health and minimal chemical exposures was compared to two groups of patients diagnosed with health problems following exposure to pesticides or to organic solvents.

La maladie d'Alzheimer (MA) est une maladie neurodégénérative caractérisée par la présence d'enchevêtrements neurofibrillaires et de plaques séniles. Le composant majoritaire des plaques séniles est le peptide amyloïde Aβ.Dans une première partie de cette thèse, l'objectif a été de caractériser la toxicité du peptide Aβ25-35 après son injection au niveau des ventricules latéraux chez le rat au cours du temps. Nous avons ainsi pu démontrer, entre autre, qu'une seule injection, engendre des déficits mnésiques à court et à long terme qui persistent six semaines après l'injection. Nous avons également montré, entre autre, une astrogliose, une microgliose, une élévation du stress oxydant, ainsi que des phénomènes apoptotiques dans les différentes structures cérébrales étudiées. Le deuxième objectif de cette thèse a été de caractériser le rôle du peptide Aβ25-35 dans la régulation de l'axe hypothalamo-hypophyso-surrénalien (HPA) au cours du temps. Dans un premier temps nous avons démontré une hyperactivité de l'axe, qui se caractérise par une modification de l'expression des hormones et une modification d'expression et de localisation des récepteurs aux glucocorticoïdes (GC). Nous avons montré que l'injection d'Aβ25-35 induisait un comportement anxieux. Néanmoins la fonctionnalité du rétrocontrôle négatif des GC reste intacte. Alors que l'injection de l'Aβ25-35 modifie la réponse de l'axe HPA à un stress. Nos résultats, dans un modèle pathomimétique, de la MA, montrent que la toxicité amyloïde modifie la fonctionnalité et la réactivité de l'axe HPA, ce qui pourrait participer à la pathophysiologie de la MA. / Alzheimer's disease (AD) is characterized by neurofibrillary tangles and seniles plaques. The major component of senile plaques is the amyloid-β peptide (Aβ). In a first part of this thesis, we characterized the time course toxicity effect of the Aβ25-35 intracerebroventricular (icv) injection in the rat brain. We particulary demonstrated, that only one injection induced memories impairments at short and long term which persisted six weeks after the icv injection. We also shown, a sustain astrogliosis and microgliosis, oxidative stress, apoptotics processes in the differents brain structure of interest.In a second part of this thesis, we characterized the time course impact of Aβ25-35 on hypothalamo-pituitary-adrenal axis during the time. First, we demonstrated an the hyperactivity of the axis, which is characterized by modifications of hormonal concentration associated with modification of the expression and localization of glucocorticoids (GC) receptors. We also demonstrated Aβ25-35 an anxious behavioural in animals. Nevertheless, the functionality of negative feedback is not modified. However, Aβ25-35 injection modify the HPA axis reactivity after acute stress. In conclusions, we shown, in a pathomimetic model of AD that the Aβ25-35 toxicity modifes the reactivity and the functionality of HPA axis, that could be partly involved in the pathophysiology of AD.

Toxinas animais são moléculas aplicáveis na geração de agentes terapêuticos e/ou de ferramentas experimentais para a pesquisa básica e aplicada, justificando sua purificação e análise funcional. Considerando que estudos de venenos de sapos são relevantes, por serem estes considerados uma boa fonte de toxinas que atuam sobre diferentes sistemas biológicos, os objetivos deste trabalho foram isolar toxinas presentes no veneno de Rinella schneideri e avaliar suas ações sobre a atividade da enzima Na+K+-ATPase e os sistemas nervosos central e periférico. O veneno de Rhinella schneideri foi inicialmente submetido a diferentes extrações resultando em quatro amostras. A AMOSTRA A, que apresenta apenas componentes de baixa massa molecular, foi a mais efetiva na redução da atividade da Na+K+-ATPase e foi, portanto, liofilizada e submetida a uma cromatografia de fase reversa em sistema CLAE em coluna C2C18. Das 5 frações majoritárias obtidas nesta cromatografia apenas as Rs3, Rs4 e Rs5 induziram uma redução concentração-dependente da atividade da Na+K+-ATPase, mostrando IC50% de 33,6 g, 47,7 g e 98,92 g, respectivamente. Estes resultados indicam que o veneno de R. schneideri apresenta pelo menos três substâncias capazes de inibir a Na+K+-ATPase. As frações Rs3, Rs4 e Rs5, foram submetidas à espectrometria de massa e revelaram massas moleculares de 403, 401 e 387 Da, provavelmente correspondentes à Telocinobufagina, Desacetilcinobufagina e Bufalina, respectivamente. Estes compostos mostraram também neuroproteção central muito relevante sobre crises convulsivas induzidas por PTZ (Pentilenotetrazol) e NMDA (n-metil-d-aspartato), sendo que a Rs5 foi a que causou maior neuroproteção. No entanto, estas mesmas frações apresentaram ação neurotóxica periférica, induzindo bloqueio da junção neuromuscular de pintainhos. Manifestações como alucinações, dormência, confusão mental também são observadas em envenenamentos por sapos, que podem ser induzidos por alcalóides presentes no veneno, o que justifica os estudos para a identificação dos mesmos. Neste trabalho confirmou-se a presença de ii alcalóides no veneno. No entanto, foram priorizados os estudos com as toxinas isoladas Rs3, Rs4 e Rs5, por apresentarem ações biológicas importantes. Concluindo, neste trabalho foram isolados 3 compostos de baixa massa molecular, denominados Rs3, Rs4 e Rs5, que são capazes de inibir a atividade da Na+K+- ATPase, bloquear a transmissão do impulso nervoso na junção neuromuscular de pintainhos e, principalmente a Rs5, proteger crises convulsivas induzidas por PTZ e NMDA. Estudos adicionais serão necessários para estabelecer a correlação entre estes efeitos e determinar o mecanismo de ação destas toxinas. / Animal toxins are molecules applicable in the generation of therapeutic agents and / or experimental tools for basic and applied research, justifying its purification and functional analysis. Whereas studies of poison toads are relevant, since these are considered a good source of toxins that act on different biological systems, the objectives of this work were to isolate toxins in the venom of Rinella schneideri and evaluate their actions on the Na+K+-ATPase activity and the central and peripheral nervous systems. The venom Rhinella schneideri was initially submitted to different extractions resulting in four samples. The SAMPLE A, with only low molecular mass components, was the most effective in reducing the activity of Na+K+-ATPase and was lyophilized and subjected to reverse phase chromatography in the HPLC system in C2C18 column. Five majority fractions were obtained from this chromatography and only Rs3, Rs4 and Rs5 induced a concentration-dependent reduction in activity of Na+K+-ATPase, showing IC50% 33.6 g, 47.7 g and 98.92 g, respectively. These results indicate that R. schneideri venom presents at least three substances that can inhibit the Na+K+-ATPase. Fractions Rs3, Rs4 and Rs5 were submitted to mass spectrometry assay showing molecular masses of 403, 401and 387 Da, probably corresponding to Telocinobufagin, Desacetylcinobufagin and Bufalin, respectively. These compounds also showed a very relevant central neuroprotection on seizures induced by PTZ (Pentylenetetrazole) and NMDA (N-methyl-d-aspartate), and the Rs5 caused the highest neuroprotection. However, these same fractions showed neurotoxicity on peripheral nervous system, inducing blockade of the neuromuscular junction of chicks. Manifestations such as hallucinations, numbness, mental confusion are also seen in poisoning by toads, which can be induced by alkaloids present in the venom, which justifies the studies for their identification. This work confirmed the presence of alkaloids in the venom. However, have been prioritized the studies with isolated toxins Rs3, Rs4 and Rs5, because they have important biological actions. In conclusion, in this study were isolated three compounds with iv low molecular mass, known as Rs3, Rs4 and Rs5, which are capable of inhibiting the activity of Na+K+-ATPase, blocking the nerve impulse transmission at the neuromuscular junction of chickens, and especially the Rs5 by protecting seizures induced by PTZ and NMDA. Additional studies are necessary to establish the correlation between these effects and determine the mechanism of action of these toxins.

The dinoflagellate Karenia brevis is one organism responsible for harmful algal blooms (HABs) that severely impact marine life. K. brevis produces a suite of neurotoxins referred to as brevetoxins (PbTx) which bind to voltage-gated sodium channels (VGSCs) in excitable tissues, affecting cellular permeability leading to a suite of symptoms and potentially cell death. Brevetoxicosis is difficult to treat in sea turtles as the physiological impacts have not been investigated and the magnitude and duration of brevetoxin exposure are generally unknown. Due to their threatened and endangered status, experimental exposures cannot be performed to determine the fate of brevetoxin in sea turtle tissues, making it difficult to design appropriate treatments. The freshwater turtle, Trachemys scripta, was utilized as a model for brevetoxin exposure in turtles. Turtles were exposed to intratracheal instillation (10.53μg/kg) or oral dosing (33.48μg/kg) of PbTx-3 3x weekly over a period of 2-4 weeks. Tissues and fluids were collected for ELISA to determine PbTx-3 uptake and distribution, routes of excretion and rates of clearance (1h-1wk post-exposure). Tissues were also preserved for histopathology. Primary turtle neuronal cell cultures were exposed to PbTx-3 in the presence and absence of various agonists and antagonists to determine brevetoxin’s mode of action. PbTx-3 was widely distributed in all tissues and fluids following both intratracheal and oral exposures, but was largely cleared from the system within 24 hours; PbTx-3 moved into the bile and feces over 48h post exposure indicating that this is the main route of excretion. While exposed animals showed clear behavioral symptoms of toxicity including muscle twitching, swimming in circles, and ataxia, there was no evident tissue pathology. Despite the evident behavioral effects, turtle neurons are surprisingly resistant to PbTx-3, with an EC50 significantly higher than is seen in mammalian neurons. While PbTx-3 exposure resulted in significant Ca2+ influx, various antagonists prevented Ca2+ influx when added with PbTx-3 confirming the mechanism of action through VGSCs. Upregulation of Hsp72 in the turtle brain could be enhancing cell survival. Based on results, intralipid treatment post PbTx-3 exposure rapidly decreases symptoms and proves to be a suitable treatment for toxin exposure. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

A exposição a agentes químicos neurotóxicos pode concorrer para o desenvolvimento ou potencialização de dificuldades de aprendizagem. A investigação dos níveis de concentração de metais pesados em escolares com tais dificuldades pode auxiliar no planejamento terapêutico, bem como orientar órgãos de saúde competentes para promoção de prevenção e de desintoxicação. Foi realizado um estudo com o objetivo de verificar as concentrações remotas de chumbo em escolares com dificuldades de aprendizagem, a fim de avaliar a prevalência de exposição precoce a este agente, bem como correlacionar os níveis encontrados com resultados de desempenhos em avaliações de processamento fonológico, leitura, escrita e aritmética, além de descrever estatisticamente a amostra quanto a aspectos relevantes do histórico clínico e identificar os bairros de origem ao nascimento. Participaram escolares na faixa etária de 9 a 14 anos, regularmente matriculados no Ensino Básico de instituições públicas ou privadas do município de Bauru (SP) e região, em atendimento na Clínica de Linguagem Escrita da FOB-USP. Foram utilizadas amostras de esmalte dentário superficial como biomarcador de exposição remota ao chumbo. Foram realizadas análises por espectrometria de absorção atômica de forno de grafite (GF AAS) para determinação do chumbo e espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) para determinação do fósforo, necessário para o cálculo da massa de esmalte. O estudo teve 17 participantes. Os resultados indicam a prevalência de 100% de exposição precoce ao chumbo, média da concentração de 46,56 g Pb/g esmalte, DP = 47,09. Não houve correlações estatisticamente significativas com os desempenhos avaliados. Quanto ao perfil amostral, as meninas representam 17,6% e os meninos 82,4%. Um total de 35,3% dos participantes sofreram intercorrências gestacionais ou neonatais, 23,5% tem QI limítrofe ou rebaixado, 94,1% tem histórico de distúrbios de linguagem oral, 41,2% alterações psicomotoras, 5,9% diagnosticados com TDAH. A análise descritiva qualitativa dos bairros de origem revela que a distribuição dos mesmos está dispersa pelo município, além de participantes de outras localidades da região. / Exposure to neurotoxic chemical agents may contribute to the development or enhancement of learning disabilities. The investigation of concentration levels of heavy metals in schoolchildren with such difficulties can aid in therapeutic planning as well as guide competent health agencies to promote prevention and detoxification. A study was carried out with the objective of verifying the remote concentrations of lead in students with learning disabilities in order to evaluate the prevalence of early exposure to this agent, as well as to correlate the levels found with results of performances in phonological processing evaluations, reading, writing and arithmetic, in addition to statistically describing the sample regarding relevant aspects of clinical history and identifying origin neighborhoods at birth. Participants were students aged 9 to 14 years, regularly enrolled in Basic Education of public or private institutions of the municipality of Bauru (SP) and region, attending the Clinic of Written Language of FOB-USP. Surface dental enamel samples were used as a biomarker for remote lead exposure. Analyzes were performed by atomic absorption spectrometry of graphite furnace (GF AAS) for determination of lead and inductively coupled plasma optical emission spectrometry (ICP OES) for determination of phosphorus, necessary for the calculation of enamel mass. The study had 17 participants. The results indicate the prevalence of 100% early exposure to lead, mean concentration of 46.56 g Pb / g enamel, SD = 47.09. There were no statistically significant correlations with the evaluated performances. The sample profile reveals that girls represent 17.6% and boys 82.4%. A total of 35.3% of the participants had gestational or neonatal intercurrences, 23.5% had borderline or reduced IQ, 94.1% had a history of oral language disorders, 41.2% had psychomotor disturbances, 5.9% had ADHD. The qualitative descriptive analysis of the origin neighborhoods reveals that its distribution is dispersed by the municipality, besides participants of other localities of the region.

Harmful algal blooms (HABs, or "red tides") of the brevetoxin-producing dinoflagellate Karenia brevis occur periodically along Florida's Gulf coast. Mass mortalities of marine birds have long been associated with these blooms, yet there are few data documenting the accumulation of brevetoxins (PbTx) in the tissues of birds. Post-mortem evaluations were performed on 185 birds representing 22 species collected from October 2001 through May 2006 during red tide and non-red tide events to quantify their body burdens of brevetoxins. A variety of tissues and organs were selected for brevetoxin analysis including blood, brain, heart, fat, stomach or gut contents, intestinal contents or digestive tract, muscle, lung, liver or viscera, kidney, gonads, gallbladder and spleen. Brevetoxin levels in avian tissues ranged from K. brevis which may amass in various tissues of the body. As a consequence, the birds may exhibit acute brevetoxicosis during red tide events or show chronic accumulation effects during non-red tide events.

Abstract not available

Thesis (M.Sc. (Pharmacy)) - Rhodes University, 2008.

Thesis (M.Sc. (Pharmacy)) - Rhodes University, 2008.