Thesis (Ph.D.)--Mississippi State University. College of Veterinary Medicine. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 174-200).

AIDS Dementia Complex (ADC) is a neurodegenerative disorder implicated in HIV-1 infection that is associated with elevated levels of the neurotoxin, quinolinic acid (QA) which causes a cascade of events to occur, leading to the production of reactive oxygen species (ROS), these being ultimately responsible for oxidative neurotoxicity. In clinical studies, Non-nucleoside reverse transcriptase inhibitors (NNRTIs), efavirenz (EFV) and nevirapine (NVP) have been shown to potentially delay the progressive degeneration of neurons, thus reducing the frequency and neurological deficits associated with ADC. Despite these neuroprotective implications, there is still no biochemical data to demonstrate the mechanisms through which these agents offer neuroprotection. The present study aims to elucidate and further characterize the possible antioxidant and neuroprotective mechanisms of NVP and EFV in vitro and in vivo, using QA-induced neurotoxicity as a model. Research has demonstrated that antioxidants and metal chelators have the ability to offer neuroprotection against free radical induced injury and may be beneficial in the prevention or treatment of neurodegeneration. Hence the antioxidant and metal binding properties of these agents were investigated respectively. Inorganic studies, including the 1, 1-diphenyl-2 picrylhydrazyl (DPPH) assay, show that these agents readily scavenge free radicals in vitro, thus postulating the antioxidant property of these agents. The enhancement of superoxide radical generation and iron mediated Fenton reaction by QA is related to lipid peroxidation in biological systems, the extent of which was assayed using the nitroblue tetrazolium and thiobarbituric acid method respectively. Both agents significantly curtail QA-induced lipid peroxidation and potentially scavenge superoxide anions generated by cyanide in vitro. Furthermore, in vivo results demonstrate the ability of NVP and EFV to protect hippocampal neurons against lipid peroxidation induced by QA and superoxide radicals generated as a consequence thereof. The alleviation of QA-induced oxidative stress in vitro possibly occurs through the binding of iron (II) and / or iron (III), and this argument is further strengthened by the ability of EFV and not NVP to reduce iron (II)-induced lipid peroxidation in vitro directly. In addition the ferrozine and electrochemistry assay were used to measure the extent of iron (II) Fe[superscript 2+] and iron (III) Fe[superscript 3+] chelation activity. Both assays demonstrate that these agents bind iron (II) and iron (III), and prevent redox recycling of iron and subsequent complexation of Fe[superscript 2+] with QA which enhances neuronal damage. Both NNRTIs inhibit the endogenous biosynthesis of QA by inhibiting liver tryptophan 2, 3-dioxygenase activity in vivo and subsequently increasing hippocampal serotonin levels. Furthermore, these agents reduce the turnover of hippocampal serotonin to 5-hydroxyindole acetic acid. NVP and not EFV increase 5-hydroxyindole acetic acid and norepinephrine levels in the hippocampus. The results of the pineal indole metabolism study show that NVP increases the synthesis of melatonin, but decreases N-acetylserotonin, 5-hydroxyindole acetic acid and 5-hydroxytryptophol levels. Furthermore, it shows that EFV decreases 5-hydroxyindole acetic acid and melatonin synthesis. Behavioural studies using a Morris water maze show that the post-treatment of rats with NVP and EFV significantly improves QA-induced spatial memory deficits in the hippocampus. This study therefore provides novel information regarding the neuroprotective mechanisms of NVP and EFV. These findings strengthen the argument that these NNRTIs not only have antiviral effects but possess potential neuroprotective properties, which may contribute to the effectiveness of these drugs in the treatment of ADC.

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.

Orientadores: Lea Rodrigues Simioni, Yoko Oshima Franco / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-09T01:04:42Z (GMT). No. of bitstreams: 1 Ferreira_SandroRostelato_M.pdf: 1413633 bytes, checksum: 6030097384697994f16895f8fb1a4c92 (MD5) Previous issue date: 2007 / Resumo: O veneno de Bothrops jararacussu (Bjssu) e sua miotoxina bothropstoxina-I (BthTX-I), induzem neurotoxicidade e miotoxicidade. Como o tratamento com o antiveneno é pouco eficaz contra a miotoxicidade, muitos estudos têm sido realizados utilizando substâncias que neutralizem a atividade miotóxica induzida pelo veneno, entre elas, a heparina. Os objetivos deste trabalho foram: 1) verificar o efeito da heparina sobre a miotoxicidade induzida pelo veneno e toxina, utilizando-se uma baixa concentração de heparina, porém capaz de impedir o bloqueio neuromuscular e, 2) esclarecer o papel protetor da heparina contra Bjssu. Controles foram realizados com antiveneno botrópico (AVB) comercial ou solução nutritiva de Tyrode ou salina. Para avaliar a neurotoxicidade empregou-se técnica miográfica convencional em preparações nervo frênico-diafragma de camundongos (in vitro) e nervo ciático poplíteo externo-tibial anterior de ratos (in vivo); para avaliar a miotoxicidade in vitro empregou-se a técnica histológica (microscopia óptica) e in vivo a dosagem bioquímica da creatinoquinase (CK); para avaliar o papel protetor da heparina empregou-se a protamina, um antagonista farmacológico. Os resultados obtidos in vitro mostraram que a resposta contrátil de 12 ± 2% (n=6) frente à incubação com Bjssu (40 µg/mL) por 120 min foi aumentada para 79,6 ± 5,9% (n=6) quando pré-incubado com heparina (5 UI/mL) e 68,3 ± 6,2% (n=6) quando pré-incubado com AVB (120 µL/mL); na mesma situação a BthTX-I (2,9 µM) passou de 5 ± 1,3% (n=8) para 78,8 ± 6,8% (n=8) com heparina e 62,3 ± 6,1% (n=6) com AVB. A média da quantificação do dano morfológico (leitura de três diferentes observadores) mostrou que o veneno provocou lesões de 27% e a toxina de 40%, que passaram para níveis de 5% e 9%, respectivamente, quando tratadas com heparina e 11% e 3% quando com AVB. Os pré-tratamentos não apresentaram diferença significativa em relação ao controle Tyrode. Os resultados in vivo (em ratos) mostraram que as mesmas concentrações de veneno e toxina utilizadas nos ensaios in vitro não provocaram alterações na resposta contrátil; contudo, quando injetados no músculo gastrocnêmio de camundongos, apresentaram níveis plasmáticos de CK (U/L) de: 1454 ± 185 (Bjssu, n=6) diminuindo (P<0,05) para 236 ± 40 (com heparina, n=6) e 47 ± 5 (com AVB, n=6); 1531 ± 166 (BthTX-I, n=5) diminuindo (P<0,05) para 900 ± 149 (com heparina, n=5) e 935 ±135 (com AVB, n=5). A adição de protamina (0,8 UI/mL) aos 15 minutos de incubação da mistura heparina + veneno causou o bloqueio neuromuscular característico do veneno em preparações in vitro. Conclui-se que a heparina é mais eficaz (mas pode ser totalmente bloqueada pela protamina) que o AVB quanto a sua capacidade de impedir a neurotoxicidade in vitro causada por Bjssu e BthTX-I, e que nas mesmas concentrações a heparina demonstrou nenhuma neurotoxicidade in vivo (ratos) e que ela é tão eficiente quanto o AVB na miotoxicidade in vitro, mas menos eficaz in vivo em relação ao veneno bruto / Abstract: Bothrops jararacussu venom (Bjssu) and its myotoxin bothropstoxin-I (BthTX-I) induce neurotoxicity and myotoxicity. Since the treatment with the antivenom is weakly efficient against the myotoxicity, many reports concentrate on studies utilizing substances that neutralize the myotixicity activity induced by the venom, including heparin. The objectives of this work were: 1) to examine the effect of heparin on the myotoxicity induced by venom and toxin, using a low heparin concentration, capable to prevent the neuromuscular blockade and, 2) to examine the protective role of heparin against Bjssu. Control experiments were performed with commercial bothropic antivenom (CBA), Tyrode solution or saline. To examine the neurotoxicity, a conventional myoghraphic technique was used in studies with mouse phrenic nerve-diaphragm preparations (in vitro) and rat popliteal external nerve/muscle anterior tibialis (in vivo). Histological technique (light microscopy) and biochemical measurement of creatine kinase (CK) were used to examine the myotoxicity in vitro e in vivo, respectively. Protamine (a pharmaceutical antagonist) was used to evaluate the protective role of heparin. The results in vitro showed that the twitch-tension of 12 ± 2% in the presence of Bjssu (40 µg/mL; n=6) after 120 min was increased to 79.6 ± 5.9% when preincubated with heparin (5 UI/ml; n=6) and 68.3 ± 6.2% when preincubated with CBA (120 µL/mL; n=6). Similarly, the BthTX-I (2.9 µM) - induced responses amounted to 5 ± 1.3% (n=8) and 78.8 ± 6.8% with heparin (n=8) and 62.3 ± 6.1% with CBA (n=6). The quantification of morphological changes showed that the venom induced a damage of 27% and the toxin of 40%, which were reduced to 5% and 9%, when treated with heparin and 11% and 3% with CBA, respectively. The pre-treatment did not cause significant differences compared to Tyrode solution. The results in vivo showed that the same concentrations of venom and toxin utilized in in vitro assays did not induce alteration in twitch-tension. However, when injected in mouse gastrocnemius muscle, plasma levels of CK (U/l) of 1454 ± 185 (in the presence of Bjssu, n=6) were decreased to 236 ± 40 (heparin, n=6) and 47 ± 5 (CBA, n=6). Similarly, a value of 1531 ± 166 in the presence of BthTX-I (n=5) was decreased to 900 ± 149 (heparin, n=5) and 935 ±135 (CBA, n=5). The addition of protamine (0.8 UI/ml) at 15 min incubation of the mixture heparin+venom, induced a neuromuscular blockade similar to the venom in in vitro preparations. We conclude that heparin is more efficient (although totally antagonized by protamine) than CBA with respect to the in vitro neurotoxicity induced by Bjssu and BthTX-I, which did not cause myotoxicity in vivo (rats). Heparin is as efficient as CBA in myotoxicity in vitro, but less efficient in vivo compared to the crude venom / Mestrado / Mestre em Farmacologia

Dehydroepiandrosterone, a C-19 steroid, is found endogenously with the highest circulating serum levels. It is converted to important steroids such as the sex hormones oestrogen and testosterone. DHEA has come under the spotlight as a purported “fountain of youth” due to its well-characterised age-related decline. The supplementation of DHEA in both the elderly and those with a pathophysiological deficiency has been shown to be of benefit, particularly with regard to wellbeing and depression. The role of DHEA in the periphery has not been elucidated beyond its role as a precursor hormone in sex steroid biosynthesis, though it has been established as a neuroactive neurosteroid, capable of exerting neuroprotective effects in the brain. Since the importance of free radicals in aging and neurodegeneration is well established, investigations were conducted on the ability of DHEA to inhibit free radical generation or scavenge existing free radicals. DHEA was able to significantly inhibit quinolinic acid-induced lipid peroxidation, a measure of membrane damage, over a range of concentrations, although the reduction did not appear to be dose-dependent. This was observed in both in vitro and in vivo studies. Thus, the ability of a compound to reduce the degree of lipid peroxidation may indicate its value as a neuroprotectant. However, DHEA did not significantly reduce cyanide induced generation of the superoxide free radical, suggesting that DHEA is not an effective free radical scavenger of the superoxide anion and that the reduction in lipid peroxidation does not occur through a scavenging mechanism. Apoptosis is a physiological process which is necessary for development and homeostasis. However, this form of programmed cell death can be initiated through various mechanisms and too much apoptotic cell death results in deleterious effects in the body. DHEA was shown not to induce apoptosis. Even the lowest concentration of DHEA investigated in this thesis shows a remarkable decrease in the degree of apoptosis caused by intrahippocampal chemical insult by the neurotoxin quinolinic acid. Cresyl violet was used to visualise tissue for histological examination which revealed that DHEA is able to preserve the normal healthy morphology of hippocampal cells which have been exposed to quinolinic acid. Cells maintained their integrity and showed little evidence of swelling associated with necrosis. Organ culture studies were performed by assessing the impact of DHEA on several pineal metabolites. The study revealed that DHEA exerted an effect on the metabolism of indoleamines in the pineal gland. Melatonin, the chief pineal hormone, did not appear to be affected while the concentrations of N-acetylserotonin, serotonin and methoxytryptamine showed significant alterations. Thus, the neuroprotective mechanism of DHEA does not appear to be mediated by an increase in the presence of melatonin. The biological importance of metal ions in neurodegeneration is also well established and thus the potential interaction between DHEA and metal ions was considered as a mechanism of action. Spectroscopic and electrochemical analyses were performed to determine whether DHEA is able to interact with metal ions as a ligand. These reveal that DHEA does not form a strong bond with the metals investigated, namely copper (II) and iron (III), but that a weak interaction is evident. These investigations were conducted in a rodent model, which has neither large amounts of endogenous DHEA, nor the enzymatic infrastructure present in humans. Thus, the theory that DHEA exerts its effects through downstream metabolic products is unlikely. However, these investigations reveal that there is merit in the statement that DHEA itself is a neuroprotective molecule, and confirm that the further investigation of DHEA is an advisable strategy in the war against neurodegeneration and aging.

Methylenedioxymethamphetamine (MDMA) popularly known as "Ecstasy" continues to gain popularity as a recreational drug that has been shown to increase serotonin and dopamine levels. The present study has demonstrated that repeated exposure to MDMA produces long-term damage to serotonergic and dopaminergic neurons in various regions of the rat brain.