Dissertations / Theses on the topic 'Methimazol'

Olfactory sensory neurons in the olfactory epithelium are responsible for detecting the odors we smell and are constantly dying. However, in order for the sense of smell to be maintained, the olfactory system has the unique ability to generate new neurons. After an olfactory sensory neuron is born in the olfactory epithelium, it must extend an axon towards the olfactory bulb in the central nervous system. Within the olfactory bulb, these axons make specific synaptic contacts with the dendritic processes of mitral cells, which are the main projection neurons from the olfactory bulbs into higher cortical areas in the brain. In addition to regeneration due to normal turnover, the olfactory system is also capable of recovery after an injury. The olfactory system’s ability to recover is remarkable because it is capable of regeneration after a mild injury (a portion of olfactory epithelium is removed) or a severe injury (in which the entire olfactory epithelium is removed.) A well-established model for producing a severe type of injury in the olfactory epithelium is by inducing a chemical ablation by a single injection of the drug methimazole. A specific interest in the regenerative process after injury is reestablishment of synaptic connections. We hypothesized that expression of synaptic markers will allow for establishing a timeline of functional recovery of the olfactory system after injury. Our lab has studied three synaptic vesicle associated proteins, vesicular glutamate transporter -1 (VGlut-1), vesicular glutamate transporter-2 (VGlut-2), and synaptophysin, as well as one activity-regulated protein, tyrosine hydroxylase. These studies found specific temporal expression profiles at 2, 7 and 14 days post injury. Our initial data show that VGlut-1 and VGlut-2 are decreased after injury, indicative of a reduction in synaptic connectivity in both olfactory sensory neuron axons and in dendrites of mitral cell neurons. These changes in synaptic connectivity help in understanding functional connectivity after an injury and can further be used to correlate histological axonal tracing with behavioral studies.

Neurons in the olfactory epithelium that are responsible for detecting the odors we smell are constantly dying. However, the olfactory system has the unique ability to regenerate new neurons in order for the sense of smell to be maintained. After a new sensory neuron is born in the olfactory epithelium, it must extend a new axon that will travel to the olfactory bulb and make specific synaptic contact so that the odor information from the epithelium can be coded and sent to the higher cortical areas of the brain. The olfactory system’s ability to recover is also even more complex in that it is capable of regeneration after an injury in which a portion or even the entire olfactory epithelium is removed. A well established model for this type of injury in the olfactory epithelium is by inducing a chemical ablation by injection of the drug methimazole. A specific interest in the regenerative process after injury is the mechanism by which axonal debris from the dead neurons is removed. After ablation of the olfactory epithelium, the cell bodies of the neurons detach but their axons remain intact. The axonal debris must not only be removed, but must also be done so in a way that minimizes inflammation in order for new axons to be able to extend to the olfactory bulb. Axonal debris removal has been characterized both in vitro and during development. However, the mechanism of debris removal has yet to be characterized after an injury. Our lab has studied different engulfment proteins in the olfactory bulb after injury using RT-qPCR and found specific temporal expression profiles at 3, 14 and 21 days post injury. Our initial investigations involved some known engulfment proteins such as Jedi1, GULP, and Megf10. However, we found that these proteins are downregulated after an injury. Further investigation has shown that the proteins Cd11b and TLR2 are upregulated after injury. These changes in expression can begin to shed light on the mechanism of axonal debris removal after an injury and can further be used to study how inflammation is suppressed in order to allow for axon extension and synaptic contact to be reestablished.

The olfactory system is of great interest in research due to the olfactory epithelium’s regenerative capability and as a potential as a source of neural stem cells. The olfactory sensory neurons are constantly being replaced by the stem cells that lie at the base of the olfactory epithelium. These stem cells also remain intact after an injury to the epithelium and lead to the regeneration of the olfactory epithelium. We have developed a fate mapping technique to trace axonal regrowth from newly born olfactory sensory neurons using an inducible Cre-ERT2 model after chemical ablation by the drug methimazole. Our data shows that newly generated olfactory sensory neurons labeled 1 day after chemical ablation by injection of 4-HO-tamoxifen extend an axon that reaches the olfactory bulb and extend to the glomeruli in a timeline that is consistent with control mice that received 4-HO-tamoxifen but were injected with saline 1 day prior. In addition, we assessed the functional recovery of the olfactory epithelium by testing the ability of mice to find a hidden cookie after methimazole injection. Mice were tested at 3 and 14 days post methimazole. There was a severe impairment in the ability to find a hidden cookie at 3 days post methimazole. The mice tested at 14 days post methimazole showed an improvement in the ability to find the cookie but the latency to find the cookie was still significantly higher than controls. In conclusion, while we demonstrate that axons extend to the olfactory bulb and the glomeruli earlier than 14 days, our behavioral data suggest that there must be a critical number of axons that must reach each specific glomerulus to regain function of the olfactory system.

Orientador: Ernesto Jose Doltaviano
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Embora seja do conhecimento geral que os hormônios tireoidianos estão envolvidos no desenvolvimento e manutenção de vários órgãos, ainda, existem aspectos contraditórios sobre seu papel na fisiologia testicular. Com a proposta de melhor compreender a influência dos hormônios tireoidianos na manutenção testicular, este estudo teve como objetivo avaliar parâmetros biométricos, morfológicos e hormonais em ratos de várias idades, que foram induzidos experimentalmente ao hipotireoidismo com doses diárias de 0,05 mg de Methimazole, confirmado pelas dosagens de Tiroxina (T4). Neste estudo utilizaram-se 68 ratos brancos (Rattus no veraicus, variedade albino), machos e 12 fetos. Estes animais foram sub divididos em 6 grupos experimentais, de acordo com o tempo de tratamento e a data do sacrifício e denominados: Hipotireoidismo materno-fetal (19º dia de vida fetal), 8 dias de idade, 21 dias de idade, 35 dias de idade, 50 dias de idade e 90 dias de idade. Os resultados mostraram que a indução do hipotireoidismo no oitavo dia de prenhez, que corresponde ao início da organogênese do rato, não resulta em aumento da incidência de reabsorção fetal ou de malformações congênitas e também não leva a alterações no comportamento dos animais com hipotireoidismo. Em todos os grupos experimentais analisados, os animais tratados apresentaram redução significativa (p<0,05) do peso corporal em relação aos animais controles da mesma idade. A avaliação biométrica dos testículos mostrou que os animais tratados apresentaram redução significativa (p<0,05) do peso testicular, do diâmetro dos túbulos seminíferos e do volume nuclear das células de Sertoli. Apenas os fetos com 19 dias de vida intra-uterina não mostraram diferenças nos parâmetros acima citados. A morfologia dos testículos dos animais tratados mostrou atraso no início do estadiamento do ciclo do epitélio seminífero, com redução da quantidade de células germinativas e aumento do número de células degeneradas. Nos grupos experimentais 50 dias e 90 dias de idade, os animais tratados apresentaram estadiamento completo do epitélio seminífero, mas a frequência dos estádios I, VII/VIII e XIV foi menor do que a dos animais controles da mesma idade. As dosagens em duplicata da testosterona plasmática, pelo método de fluoroimunoensaio de fase sólida, não mostraram diferenças significativas entre os valores encontrados nos animais controles e tratados. Conclui-se que o hipotireoidismo prejudica acentuadamente a espermatogênese dos ratos jovens, prejuízo detectável através da redução do peso testicular, da diminuição do diâmetro dos túbulos seminíferos, do aumento de células germinativas degeneradas, do atraso da espermatogênese e da redução do volume nuclear das células de Sertoli. Nos animais tratados com 90 dias de idade, ocorre ganho consideravelmente maior do peso testicular, do diâmetro dos túbulos seminíferos em relação aos animais controles da mesma idade e aparente estabilização no volume nuclear das células de Sertoli, sugerindo ausência da participação dos hormônios tireoidianos sobre o testículo do rato adulto
Abstract: Although it is well known that thyroidal hormones are involved in the development and maintenance of many organs, there remain several open questions as to their role in testicular physiology. The present work proposes to contribute to a better understanding of the role of thyroidal hormones in testicular maintenance. The evaluation was based on the biometric, morphologic and hormonal parameters of groups of data of different ages in which a previous experimental hypothyroidism was induced by treating them with daily 0,05mg Methimazole, and confirmed by measuring thyroxine levels. Our study involved an experimental of 68 white male rats and 12 foetuses (albino Rattus novergicus). These animals were subdivided into 6 experimental groups according to the period of treatment and their death date and will here be designated as mother-foetal ( 190 days of intrauterine life), 8 day old, 21 day old, 35 day old, 50 day old and 90 day old hypothyroidism, respectively. Our results showed that induction to hypothyroidism in the eighth day of pregnancy, which corresponds to the beginning of organogenesis in rats, did not result in any increase in the incidence of either foetal reabsorption nor congenital malformations, as well not causing behavioral alteration of animals with hypothyroidism. In all of the experimental groups considered, the treated animals have a significant reduction (p<0,05) in body weight as related to the control animals of same age. Biometric evaluation of testicles has shown that treated animals had significant reduction (p<0,05) in both the testicular weight and the diameter of seminiferous tubules as well as a reduction in the nuclear volume of Sertoli cells. Only the foetuses having 19 days of intrauterine life had no differences in such parameters, while in the treated 90 day old animals testicular recuperation was observed. As to the morphology, the testicular development of treated animals was delayed in the beginning of the seminiferous epithelium cycle, with a reduction in the quantity of germinative cells and an increase in the number of degenerated cells. In both the 50 and 90 day old experimental groups, the treated animals completed staging of the seminiferous epithelium, but the frequency of stages I, VII/VIII and XIV was reduced as compared to the control animals of the same age. Duplicated dosages of plasmic testosterone by means of solid phase fluoroimunoassays showed no significant differences in the values found for both treated and control animals. We conclude that hypothyroidism severely impairs espermatogenesis in young rats as indicated by the reduced testicular weight, the diminished seminiferous tubule diameter, the increased degeneration of germinative cells, the delayed staging in the seminiferous epithelium cycle and the reduced nuclear volume in Sertoli cell. This did not occur in adults rats. In treated animals belonging to the 90 day old experimental group we have observed the occurence of significantly larger gain in both the testicular weight and the seminiferous tubule diameter, as compared to the control animals of the same age, as well as the occurrence an apparent stabilization of the nuclear volume of Sertoli cells, which thereby suggest that there is no influence of the thyroidal hormones upon adult rats testicles
Mestrado
Fisiologia
Mestre em Ciências Biológicas

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A cisplatina é um agente antineoplásico utilizado em oncologia veterinária, sendo indicada no tratamento adjuvante de várias neoplasias, contudo, sua eficácia terapêutica é, muitas vezes, limitada por seu efeito nefrotóxico e emetogênico. Neste estudo, objetivou-se avaliar um novo protocolo quimioterápico, utilizando associação do methimazole e do ondansetron à cisplatina, além de tentar minimizar o tempo de fluidoterapia. Foram utilizados 12 cães, machos, divididos em quatro grupos experimentais, sendo constituídos de três animais por grupo. Os grupos foram divididos de acordo com o tempo de fluidoterapia: G1 (sem fluidoterapia), G2 (uma hora de fluidoterapia antes da cisplatina), G3 (uma hora de fluidoterapia antes da cisplatina e uma hora após) e G4 (duas horas de fluidoterapia antes da cisplatina e uma após). Todos os animais receberam cisplatina na dose de 70 mg/m2, por via intravenosa, diluída em solução fisiológica 0,9%, e administrada por um período de 20 minutos. Os ciclos de quimioterapia foram realizados em intervalos de três semanas totalizando três ciclos. O ondansetron foi administrado na dose de 0,4 mg/kg, por via intravenosa, a cada 8 horas, no dia da quimioterapia e a seguir a cada 12 horas por dois dias, começando 30 minutos antes do início da quimioterapia. O methimazole foi administrado na dose de 40mg/kg, por via oral, 30 minutos antes da cisplatina e quatro horas após. Foram avaliados os parâmetros hematológicos, bioquímicos, urinários e dosagem de tiroxina e triiodotironina a cada sete dias até o término do experimento. Pelos resultados obtidos observou-se que este protocolo é eficaz e seguro quando os animais permanecem por um período de duas a três horas sob fluidoterapia, visto que não apresentaram alterações clínicas laboratoriais decorrentes do uso da quimioterapia...
The cisplatin is an antineoplasic agent used in veterinary oncology, being indicated to the adjuvant treatment of several neoplasms, however, its therapeutic effectiveness is, a lot of times, limited by its nephrotoxic and emetogenic effects. The objective of this study was evaluating a new chemotherapic protocol, using association of methimazole and ondansetron to the cisplatin, besides trying to minimize the time of saline diuresis. Twelve male dogs were divided in four experimental groups, being constituted of three animals by group. The groups were divided according to the time of saline diuresis: G1 (without saline diuresis), G2 (an hour of saline diuresis before the cisplatin), G3 (an hour of saline diuresis before the cisplatin and one hour after) and G4 (two hours of saline diuresis before the cisplatin and one after). All animals received cisplatin in the dose of 70 mg/m2, for intravenous road, diluted in physiologic solution 0,9%, and administered by a period of 20 minutes. The chemotherapy cycles were accomplished in intervals of three weeks with three cycles. Ondansetron was administered in the dose of 0,4 mg/kg, for intravenous road, at every 8 hours, in the day of the chemotherapy and to proceed every 12 hours for two days, beginning 30 minutes before the beginning of the chemotherapy. Methimazole was administered orally in the dose of 40mg/kg, 30 minutes before the cisplatin and four hours after. The hematological, biochemical, urinary parameters and dosage of tiroxin and triiodotironine were evaluated every seven days until the end of the experiment. It was observed that this protocol is effective and safe when the animals stay for a period of two or three hours under saline diuresis, because they didn't present clinical and laboratory alterations of the use of chemotherapy... (Complete abstract, access undermentioned eletronic address)

Orientador: Carlos Roberto Daleck
Banca: Júlio Carlos Canola
Banca: Newton Nunes
Banca: Cleuza Maria de Faria Rezende
Banca: Duvaldo Eurides
Resumo: A cisplatina é um agente antineoplásico utilizado em oncologia veterinária, sendo indicada no tratamento adjuvante de várias neoplasias, contudo, sua eficácia terapêutica é, muitas vezes, limitada por seu efeito nefrotóxico e emetogênico. Neste estudo, objetivou-se avaliar um novo protocolo quimioterápico, utilizando associação do methimazole e do ondansetron à cisplatina, além de tentar minimizar o tempo de fluidoterapia. Foram utilizados 12 cães, machos, divididos em quatro grupos experimentais, sendo constituídos de três animais por grupo. Os grupos foram divididos de acordo com o tempo de fluidoterapia: G1 (sem fluidoterapia), G2 (uma hora de fluidoterapia antes da cisplatina), G3 (uma hora de fluidoterapia antes da cisplatina e uma hora após) e G4 (duas horas de fluidoterapia antes da cisplatina e uma após). Todos os animais receberam cisplatina na dose de 70 mg/m2, por via intravenosa, diluída em solução fisiológica 0,9%, e administrada por um período de 20 minutos. Os ciclos de quimioterapia foram realizados em intervalos de três semanas totalizando três ciclos. O ondansetron foi administrado na dose de 0,4 mg/kg, por via intravenosa, a cada 8 horas, no dia da quimioterapia e a seguir a cada 12 horas por dois dias, começando 30 minutos antes do início da quimioterapia. O methimazole foi administrado na dose de 40mg/kg, por via oral, 30 minutos antes da cisplatina e quatro horas após. Foram avaliados os parâmetros hematológicos, bioquímicos, urinários e dosagem de tiroxina e triiodotironina a cada sete dias até o término do experimento. Pelos resultados obtidos observou-se que este protocolo é eficaz e seguro quando os animais permanecem por um período de duas a três horas sob fluidoterapia, visto que não apresentaram alterações clínicas laboratoriais decorrentes do uso da quimioterapia... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The cisplatin is an antineoplasic agent used in veterinary oncology, being indicated to the adjuvant treatment of several neoplasms, however, its therapeutic effectiveness is, a lot of times, limited by its nephrotoxic and emetogenic effects. The objective of this study was evaluating a new chemotherapic protocol, using association of methimazole and ondansetron to the cisplatin, besides trying to minimize the time of saline diuresis. Twelve male dogs were divided in four experimental groups, being constituted of three animals by group. The groups were divided according to the time of saline diuresis: G1 (without saline diuresis), G2 (an hour of saline diuresis before the cisplatin), G3 (an hour of saline diuresis before the cisplatin and one hour after) and G4 (two hours of saline diuresis before the cisplatin and one after). All animals received cisplatin in the dose of 70 mg/m2, for intravenous road, diluted in physiologic solution 0,9%, and administered by a period of 20 minutes. The chemotherapy cycles were accomplished in intervals of three weeks with three cycles. Ondansetron was administered in the dose of 0,4 mg/kg, for intravenous road, at every 8 hours, in the day of the chemotherapy and to proceed every 12 hours for two days, beginning 30 minutes before the beginning of the chemotherapy. Methimazole was administered orally in the dose of 40mg/kg, 30 minutes before the cisplatin and four hours after. The hematological, biochemical, urinary parameters and dosage of tiroxin and triiodotironine were evaluated every seven days until the end of the experiment. It was observed that this protocol is effective and safe when the animals stay for a period of two or three hours under saline diuresis, because they didn't present clinical and laboratory alterations of the use of chemotherapy... (Complete abstract, access undermentioned eletronic address)
Doutor

Dissertação de Mestrado Integrado em Medicina Veterinária
This thesis is constituted by one retrospective study and one prospective study of the hyperthyroid cat population of the Wylie Veterinary Centre. The retrospective study was based on 266 hyperthyroid cats presented in the practice from 1/8/07 to 31/7/09, with the objective of characterizing the population and evaluating the efficacy and safety of the different therapeutic options. The therapeutic options were surgery and medical therapy with Neo-mercazole® (carbimazole), Felimazole® (methimazole), methimazole liquid and Vidalta® (sustained release carbimazole). Methimazole liquid was the most effective option, controlling 69,2% of the cases. Because it is no longer available, the most effective available option is the unilateral thyroidectomy, with 69% of controlled cases. Neo-mercazole® and methimazole liquid were the safest options, without causing adverse reactions. However, because they are no longer available, the safest option is probably the unilateral thyroidectomiy, with only 4,8% of complications. Comparing the available medical options, Vidalta® seems to be the most effective, with 54,9% of controlled cases, and Felimazole® the safest, causing adverse reactions in 5,13% of the cases. Comparing the costs of the different treatment options, medical therapy requires a lower initial investment, but thyroidectomy seems to be the most economical long-term option, corresponding to a oneyear course of medical treatment and to half the price of radioiodine therapy. The prospective study involves the 77 hyperthyroid cats seen in a period of 3 months. The population was characterized, the frequency of the clinical signs, hematologic and biochemical changes was determined, as well as the outcome of medical and surgical therapy and the involvement of the parathyroid in surgery. The extracted thyroid glands and submitted to histopathology. The population had a mean of 14 years of age. 18 new cases were diagnosed, corresponding to 6 new hyperthyroid cats per month. All cats presented weight loss. The frequency of diarrhoea, dyspnoea, heart murmur, PU/PD, skin lesions and vomiting was much lower than described the in literature, as well as the frequency of erythrocytosis, increased liver enzymes and hyperphosphatemia. Azotemia had a higher frequency than described in the literature and de novo azotemia happened after treatment in 15,6% of the cases. The incidence of side effects of treatment was 23,38%. The most frequent concomitant disease was dental disease and the most common diagnostic complementary exam was echocardiography. The only patient that died of a complication from surgery was submitted to a simultaneous bilateral surgery. In 2 of the 7 thyroidectomies the parathyroid’s blood supply was not preserved. Thyroid carcinoma was found in 3 of the 7 analysed glands.
RESUMO - Este trabalho é constituído por um estudo retrospectivo e um estudo prospectivo da população de gatos hipertiroideus do hospital veterinário Wylie Veterinary Centre, no Reino Unido, Foi feito um estudo retrospectivo dos 266 casos apresentados no Wylie Veterinary Centre entre 1/8/07 e 31/7/09, com o objectivo de caracterizar a população e avaliar a eficácia e segurança das várias opções terapêuticas. As opções terapêuticas foram tiroidectomia e terapêutica médica com Neo-mercazole® (carbimazol), Felimazole® (metimazol), metimazol líquido e Vidalta® (carbimazol de libertação contínua). Metimazol líquido foi a opção mais eficaz, controlando 69.2% dos casos. Por não se encontrar disponível, a opção disponível mais eficaz é a tiroidectomia unilateral, com 69% de casos controlados. Neo-mercazole® e metimazol líquido constituem as opções mais seguras, não tendo registado quaisquer reacções adversas. Contudo, por já não estarem disponíveis, a opção disponível mais segura é a tiroidectomia unilateral, com apenas 4,8% de complicações. Comparando as opções terapêuticas médicas disponíveis, Vidalta® parece ser o mais eficaz, com 54,9% dos casos controlados e Felimazole® o mais seguro, com 5,13% de reacções adversas. Comparando os custos das opções terapêuticas, a terapêutica médica requer um menor investimento inicial. A tiroidectomia parece ser a mais económica a longo prazo, correspondendo ao custo de um ano de terapêutica médica e a metade do preço de tratamento com iodo radioactivo. Foi feito um estudo prospectivo dos 77 gatos hipertiroideus apresentados num período de 3 meses. A população foi caracterizada e foi determinada a frequência dos sinais clínicos, alterações hematológicas e bioquímicas, bem como os resultados obtidos com as terapêuticas médica e cirúrgica. As tiróides extirpadas foram submetidas a análise histopatológica. A média de idades da população foi de 14 anos. Foram diagnosticados 18 novos casos, o que corresponde a 6 novos casos por mês. Todos os casos apresentaram perda de peso. A frequência de ocorrência de diarreia, dispneia, sopros cardíacos, PU/PD, lesões cutâneas e vómitos foi acentuadamente mais baixa que a descrita na bibliografia, bem como a frequência de eritrocitose, elevação das enzimas hepáticas e hiperfosfatémia. A frequência de azotémicos foi superior à descrita na literatura e ocorreu azotémia de novo em 15,6% dos casos. Houve efeitos secundários à terapêutica em 23,38% dos casos. A doença concomitante mais frequente foi a patologia dentária e o meio de diagnóstico complementar mais utilizado foi a ecocardiografia. A única morte devida a uma complicação pós-cirúrgica ocorreu após uma tiroidectomia bilateral não faseada. Em 2 das 7 tiroidectomias não foi possível preservar o aporte sanguíneo da paratiroide. 3 das 7 glândulas analisadas apresentaram carcinomas.

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A glândula tireoide é uma das maiores glândulas do corpo, responsável pela produção de triiodotironina (T3) e tiroxina (T4), hormônios responsáveis pela homeostase do organismo. A redução na produção destes hormônios leva a um quadro de hipotireoidismo. O hipotireoidismo é uma desordem endócrina, mais prevalente no sexo feminino, e que pode causar uma série de alterações comportamentais e neurológicas, dentre elas a depressão. O flavonoide crisina, presente no maracujá do mato, própolis e mel de abelha, vem sendo estudado a alguns anos, sendo relatados seus efeitos antioxidantes, anticancerígenos, antihiperglicêmicos, ansiolíticos, e atualmente tem-se demonstrado sua atividade antidepressiva. O objetivo deste estudo foi investigar a ação terapêutica da crisina em modelo tipo depressivo induzido pelo hipotireoidismo em camundongos fêmeas C57BL/6 adultas. Primeiramernte os animais foram divididos em dois grandes grupos (n=20): controle e hipotireoidismo. O hipotireoidismo foi induzido por exposição contínua ao fármaco antitireoideo metimazol (MTZ) 0,1% + 0,475% de sucralose, durante 31 dias na água. No 31º dia foi retirado sangue da veia caudal e determinado os níveis de T3 e T4. Após os animais foram separados em quatro grupos (n=10): controle, hipotireoidismo, crisina, hipotireoidismo + crisina. A crisina (20mg/kg) foi administrada diariamente por 28 dias, via oral. Ao final do tratamento, os animais passaram por testes comportamentais de campo aberto (TCA), nado forçado (TNF) e suspensão de cauda (TSC), após realizou-se eutanásia nos animais, e coletou-se o sangue por punção cardíaca para análise bioquímica de T3 e T4, e retirou-se as estruturas cerebrais hipocampo e córtex pré frontal, para análises neuroquímicas de serotonina (5-HT), dopamina (DA), norepinefrina (NA). Nossos resultados demonstraram que os animais com hipotireoidismo apresentaram um aumento no tempo de imobilidade nos testes de TNF e TSC e a crisina foi capaz de reverter este tempo em ambos os testes. Demonstrou-se também que a crisina foi capaz de restaurar os níveis de neurotransmissores: 5-HT em ambas estruturas cerebrais e DA no hipocampo dos animais com hipotireoidismo, corroborando com os resultados dos testes comportamentais, nos quais o TNF está relacionado com o sistema serotoninérgico e o TSC com o sistema dopaminérgico. Em conclusão, nossos resultados demonstram pela primeira vez que a crisina é capaz de reverter o estado tipo depressivo induzido pelo hipotireoidismo, possivelmente por normalizar os níveis de 5-HT e DA.
The thyroid gland is one of the largest glands in the body, it produces triiodothyronine (T3) and thyroxine (T4), these hormones are responsible for body homeostasis. The reduction in the production of these hormones leads to hypothyroidism. The hypothyroidism is an endocrine disorder, more prevalent in females, which can cause a number of behavioral and neurological changes, including depression. The chrysin flavonoid present in the passion fruit of the bush, propolis and bee honey, has been studied for some years, being reported your antioxidant effect, anticancer, antihyperglycemic, anxiolytic, and currently your antidepressant activity was demonstrated. The objective of this study was to investigate the therapeutic action of chrysin in a model of like-depression induced by hypothyroidism in adult C57BL/6 female mice. First, the animals were divided into two groups (n=20): control and hypothyroidism. Hypothyroidism was induced by continuous exposure to the antithyroid drug methimazole (MTZ) 0.1% + 0.475% sucralose for 31 days on water. On the 31st day blood was drawn from the caudal vein and T3 and T4 levels were determined. After the animals were separated into four groups (n=10): control, hypothyroidism, chrysin, hypothyroidism + chrysin. The treatment of chrysin (20mg/kg) was administered daily for 28 days, orally. At the end of treatment the animals they passed for behavioral tests of open field test (OFT), forced swimming test (FST) and tail suspension test (TST), performed euthanasia in the animals, and collected the blood by cardiac puncture for biochemical analyze of T3 and T4, and the hippocampus and prefrontal cortex brain structures were removed for neurochemical analyzes of serotonin (5-HT), dopamine (DA), norepinephrine (NA). Our results demonstrated that animals with hypothyroidism showed an increase in the time of immobility in the tests of FST and TST and the chrysin was able to reverse this time in both tests. It was also demonstrated that the chrysin was able to restore the levels of neurotransmitters: 5-HT in both structures cerebral and DA in the hippocampus of animals with hypothyroidism, corroborating with the results of behavioral tests, in which FST is related to the serotonergic system and the TST with the dopaminergic system. In conclusion, our results demonstrate for the first time that chrysin is able of reversing the depressive-induced state induced by hypothyroidism, possibly by normalizing 5-HT and DA levels.

The flavin-containing monooxygenases (FMO
E.C.1.14.13.8) are microsomal NADPH and oxygen-dependent flavoprotein enzymes that catalyze the oxidation of a wide variety of xenobiotics, including drugs and environmental toxicants. Nucleophiles containing nitrogen, sulfur, phosphorus and selenium heteroatoms are the substrates of FMO. Bovine liver microsomal FMO enzyme activity was characterized using methimazole as substrate, which is a highly specific substrate for FMO. From 12 different bovine liver samples, microsomes were prepared and the average specific activity of bovine liver microsomal FMO was found to be 2.37 &
#61617
0.30 nmol/min/mg (Mean &
#61617
SE, n=12). The rate of reaction was linear up to 0.5 mg of bovine liver microsomal protein. The maximum FMO enzyme activity was detected at 37 &
#61616
C and at pH 8.0. Effects of detergents
Triton X-100 and Emulgen 913, on FMO activity were determined and found that enzyme activity increased by the addition of either detergent at all concentrations (0.1%-1.0%). The apparent Vmax and Km values of bovine liver microsomal FMO for methimazole substrate were found as 1.23 nmol/min/mg and 0.11 mM, respectively. Thermostability of bovine liver microsomal FMO was studied at four different temperatures
24 &
#61616
C, 37 &
#61616
C, 50 &
#61616
C and 65 &
#61616
C. The incubation time required for the complete loss of enzyme activity was 5 minutes at 65 &
#61616
C, 10 minutes at 50 &
#61616
C and 6.5 hours at 37 &
#61616
C. 68 % of the activity was still detectable at the end of 53 hours at 24 &
#61616
C. Bovine liver microsomal activity towards two drug substrates, imipramine and chlorpromazine, was also determined and found to be 3.73 and 3.75 nmol NADPH oxidized/min/mg, respectively. Effects of two drug substrates, imipramine and chlorpromazine, on bovine liver microsomal FMO-catalyzed methimazole oxidation activity was also studied and found that they inhibit FMO activity at all concentrations studied. Modulation of bovine liver microsomal FMO activity was studied using three different heavy metal ions
Ni+2, Cd+2 and Hg+2. At all other concentrations studied for each heavy metal ion and at all substrate methimazole concentrations (0.1, 0.2, 0.5, 1.0 mM), FMO-catalyzed methimazole oxidation activity decreased compared to control activity. KI values for Ni+2, Cd+2 and Hg+2 were found to be 0.5 mM, 0.085 mM, 4.6 &
#61549
M, respectively. From the Dixon plot, the pattern of inhibition for three heavy metal ions was observed to be noncompetitive.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Hypothyroidism is characterized by a disorder resulting from deficiency of thyroid hormones and is related to lipid metabolism dysfunction and cardiovascular diseases development risk. However, these changes in hypothyroidism need to be understood. Thus, this study aimed to evaluate the association between lipid, inflammatory and oxidative stress markers in patients with hypothyroidism and antioxidant effects of quercetin in these markers, using hypothyroidism experimental model induced by methimazole in rats. The methodology and results are presented in the form of articles. In article 1, were evaluated the oxidative stress biomarkers in 20 patients with subclinical hypothyroidism (SH) (49.12 ± 10.85 years). Thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT) and arylesterase (ARE) were analyzed in SH patients and controls. In addition, were measured plasmatic lipids: total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C). TBARS levels and CAT activity were higher in subclinical hypothyroidism patients, such as TC and LDL-C plasmatic levels. Arylesterase activity was lower in the SH group. Correlations were observed between plasmatic lipids and oxidative stress biomarkers and thyroid-stimulating hormone (TSH). TSH was correlated with TBARS, CAT, and SOD. The second study (manuscript 1) aimed to investigate the association between inflammatory biomarkers and overt hypothyroidism (OH). Plasmatic levels of cytokines were determinate: interleukin 1 (IL-1), interleukin 6 (IL- 6), tumor necrosis factor alpha (TNF-α), interferon gamma (INF-ɣ) and the levels of cell free DNA (cf-DNA). Furthermore, we evaluated lipid profile and prothrombotic markers (fibrinogen and D-dimer). OH patients had pro-inflammatory profile, resulted from high levels of cytokines and cf-DNA. Lipids and prothrombotic markers also showed elevated. Significant associations between inflammatory status and lipid profile were observed in hypothyroid patients. Manuscript 2 evaluates the effect of quercetin on oxidative stress biomarkers in methimazole (MMI) - induced hypothyroid rats. Hypothyroidism was induced by administering MMI at 20 mg/100 ml in the drinking water, for 30 days. After this period, rats received orally 10 or 25 mg/kg of quercetin (QT) for 8 weeks. Sixty male wistar rats were randomly divided into six groups (group I, control; group II, QT10; group III, QT25; group IV, hypothyroid; group V, hypothyroid + QT10; group VI, hypothyroid + QT25). Hypothyroid rats showed hepatic, renal and serum TBARS levels increased, along with increased protein carbonyl (PCO) in liver and increased ROS levels in liver and kidney. Quercetin administration (QT10 and 25), was effective in decreasing TBARS levels in serum and kidney, PCO in liver and ROS generation in liver and kidney tissues. Moreover, in hypothyroid group were observed high TBARS levels in cerebral cortex and hippocampus. QT25 treatment decreased the levels in both tissues. Administration of QT25 to hypothyroid rats resulted in decreased SOD activities in liver and whole blood and increased liver CAT activity. Ascorbic acid levels and total oxidative scavenging capacity (TOSC) were increased in liver and kidney rats after QT10 and QT25 treatment. These results suggest association between oxidative stress and hypothyroidism that may potentially modulated by antioxidant supplementation such as quercetin. These findings are of great importance in understanding the biochemical dysfunctions and oxidative status in hypothyroidism, as well as, in research of antioxidants strategies to be used as adjuncts in the treatment of this disorder.
O hipotireoidismo é caracterizado por uma desordem decorrente da deficiência de hormônios tireoideanos, estando relacionado a disfunções no metabolismo lipídico e ao risco de desenvolvimento de doenças cardiovasculares. Entretanto, estas alterações no hipotioreodismo precisam ser melhor compreendidas. Assim, este trabalho teve como objetivo avaliar a associação de marcadores lipídicos, inflamatórios e de estresse oxidativo em pacientes com hipotireoidismo e o efeito antioxidante da quercetina nestes marcadores, utilizando como modelo experimental o hipotireoidismo induzido por metimazol em ratos. A metodologia e resultados são apresentados sob a forma de artigos. No artigo 1, foram avaliados biomarcadores de estresse oxidativo em 20 pacientes com hipotireoidismo subclínico (HSC) (49,12 ± 10,85 anos). Os níveis de substâncias reativas ao ácido tiobarbitúrico (TBARS), e as atividades das enzimas superóxido dismutase (SOD), catalase (CAT) e arilesterase (ARE) foram determinadas em pacientes com HSC e controles. Além disso, foram investigados os níveis de lipídeos plasmáticos: colesterol total (CT), triglicerídeos (TG) e as lipoproteínas de alta (HDL) e baixa densidade (LDL). Os níveis de lipoperoxidação determinado pela medida do TBARS e a atividade da enzima CAT estavam aumentados nos pacientes hipotireóideos, bem como os níveis plasmáticos de CT e colesterol LDL. A enzima ARE mostrou-se diminuída no grupo HSC. Foram evidenciadas correlações entre lipídeos plasmáticos e biomarcadores de estresse oxidativo e com o hormônio de estimulação da tireóide (TSH). O TSH foi correlacionado com TBARS, CAT e SOD. O segundo estudo (manuscrito 1) teve por objetivo investigar a associação entre biomarcadores inflamatórios e o hipotireoidismo clínico (HC). Foram determinados os níveis plasmáticos das citocinas: interleucina 1 (IL-1), interleucina 6 (IL-6), fator de necrose tumoral alfa (TNF- α), interferon gama (INF- ɣ) e os níveis de DNA circulante livre. Além disso, foram avaliados o perfil lipídico e marcadores prótrombóticos (fibrinogênio e D-dímero). Os pacientes com HC apresentaram perfil próinflamatório, resultante dos níveis elevados das citocinas e do DNA livre. Os lipídeos e os marcadores pró-trombóticos também se apresentaram elevados. Associações significativas entre o perfil inflamatório e o perfil lipídico foram observadas nos pacientes hipotireóideos. No manuscrito 2 avaliou-se o efeito da quercetina sobre biomarcadores de estresse oxidativo em um modelo de hipotireoidismo induzido por metimazol (MMI) em ratos. O hipotireoidismo foi induzido pela administração de MMI na concentração de 20mg/100mL na água de beber, por um período de 30 dias. Após este período, os animais receberam oralmente 10 ou 25 mg/kg de quercetina (QT) por um período de 8 semanas. Ratos machos wistar (n=60) foram divididos em seis grupos (grupo I, controle; grupo II, QT10; grupo III, QT25; grupo IV, hipotireóideo; grupo V, hipotireóideo + QT10; grupo VI, hipotireóideo + QT25). Os ratos hipotireóideos apresentaram níveis de TBARS hepático, renal e séricos aumentados, bem como os níveis de proteína carbonil (PCO) no fígado e os níveis de espécies reativas de oxigênio (ERO) no fígado e rins. A administração de quercetina (QT 10 e 25) diminuiu os níveis de TBARS em soro e rins, a PCO no fígado e a geração de ERO nos tecidos hepático e renal. Além disso, no grupo hipotireóideo foram observados altos níveis de TBARS no córtex cerebral e hipocampo. O tratamento com QT25 reduziu os níveis em ambos os tecidos. A administração de QT 25 aos ratos com hipotireoidismo diminuiu a atividade da SOD em fígado e sangue total e aumentou a atividade hepática da CAT. Os níveis de ácido ascórbico e a capacidade antioxidante total aumentaram no fígado e rins dos ratos após tratamento com QT10 e QT25. O conjunto dos resultados sugeriu associação entre estresse oxidativo e hipotireoidismo que pode ser potencialmente modulado por suplementação de antioxidantes como a quercetina. Estes achados são de grande importância no entendimento das disfunções bioquímicas e do status oxidativo no hipotireoidismo como também na busca de estratégias antioxidantes a serem utilizadas como coadjuvantes no tratamento desta disfunção.

by Tsui Kai Wing.
Thesis (M.Phil.)--Chinese University of Hong Kong, 1992.
Includes bibliographical references (leaves 100-112).
Abstract --- p.i
Acknowledgements --- p.iii
List of Abbreviations --- p.iv
Contents --- p.v
Chapter Chapter 1 --- General Introduction --- p.1
Chapter Chapter 2 --- The Effect of In Vivo Methimazole Treatment on the Functions of Macrophages --- p.10
Introduction --- p.10
Materials and Methods --- p.14
Results --- p.27
Discussion --- p.38
Chapter Chapter 3 --- The Effect of In Vivo Methimazole Treatment on the Function of Lymphocytes --- p.41
Introduction --- p.41
Materials and Methods --- p.44
Results --- p.50
Discussion --- p.60
Chapter Chapter 4 --- The Lack of Demonstrable Effect of In Vitro Methimazole Treatment on the Functions of Macrophages and Lymphocytes --- p.62
Introduction --- p.62
Materials and Methods --- p.63
Results --- p.66
Discussion --- p.74
Chapter Chapter 5 --- Effect of Thyroid Hormone Replacement on the Immune Response of Methimazole-Treated Mice --- p.76
Introduction --- p.76
Materials and Methods --- p.78
Results --- p.82
Discussion --- p.91
Chapter Chapter 6 --- General Discussion --- p.95
References --- p.99

碩士
弘光科技大學
化妝品科技研究所
104
In this study, we synthesized two types of compounds containing 2-mercaptoimidazole moiety, one of which is the amino acid derivative, and the other is the kojic acid derivative. We aimed to evaluate 2-mercapto- imidazole, methimazole and the twelve synthetic compounds on inhibitory effect tyrosinase activity. Methimazole is a thiourea derivative as oral antithyroid medication and used for treatment of post inflammatory hyperpigmentation. The amino acid derivatives of 2-mercaptoimidazole and methimazole show no significant effects on tyrosinase inhibition and chelation of copper ion. Among all synthetic compounds, the kojic acid derivative from 2-mercaptoimidazole has the best inhibitory effect on tyrosinase activity. When tyrosine is used as the enzyme substrate and the IC50 value is 0.01 mM. When the substrate is L-dopa and the IC50 value is 0.15 mM. This derivative performs better inhibitory effect than kojic acid as control group and shows 31.49% chelating effects of copper ion in 1 mM. This compound is a non- competitive inhibitor. This study display that the synthetic kojic acid derivatives are easily prepared and can improve the effect of inhibiting the activity of tyrosinase. It is predicted that the 2-mercaptoimidazole and methimazole derivatives have the potential to use as whitening agents in the skin care products.

博士
國立臺灣師範大學
生命科學研究所
102
Thyroid hormones play an essential and critical role for metabolism, growth, and tissue differentiation in chordate. Thyroid dysfunction such as hypothyroidism is a frequent disease in adults, leading to neurological symptoms and emotional disease including depression. The interaction between thyroid hormones and serotonin of central nervous system may account for it. The present study was aimed to: 1. Determine the expression level of serotonin receptors including 5HT1A, 5HT2A, 5HT2C, 5HT3A, and serotonin transporter (SERT) in hippocampus, amygdala, raphe nuclei, and medial prefrontal cortex in the hypothyroid rat induced by thyroidectomy or chronic treatment of methimazole (MMI) by using real time PCR. 2. Elucidate the depression-like behavior in the chronic MMI treated rats. 3. Evaluate the hippocampal neuroplasticity in the chronic MMI treated rats. Results showed the mRNA level of 5-HT1A was increased in raphe nuclei, and the mRNAs of 5-HT2C receptor and SERT were increased in hippocampus of the thyroidectomized or MMI-treated animals. Furthermore, chronic MMI treatment also induced depression-like behavior in the rats that showed a longer time of immobility in the forced-swimming test. Additionally, the glutamatergic neuroplasity in the hippocampal CA1 region was also altered in the chronic MMI treated rats. The hippocampal LTP formation and LTD had been impaired and enhanced respectively. These changes can be restored by administration of partial glutamate NMDA receptor agonist d-cycloserine. In conclusion, we found that hypothyroid status changed expression of serotonin receptors in the raphe nuclei and limbic system, and significantly affected glutamatergic neuroplasticity. Keywords: hypothyroididm, serotonin, depression, hippocampus, LTP, forced-swimming test

Dissertação de mest., Biologia Marinha e Biotecnologia, Faculdade de Ciências do Mar e do Ambiente, Universidade do Algarve, 2007
Goitrogens are natural or synthetic compounds that suppress the function of the thyroid gland and inhibit the production of thyroid hormones (TH). Methimazole (MMI), propylthiouracil (PTU) and thiourea are used in the clinical treatment of human hyperthyroidism. Their mechanism of action in mammals is relatively well explained and such compounds have been employed in previous studies with fish to induce hypothyroidism, based upon the assumption that they work in the same way. However the action of such compounds in fish is not well studied and the effects are not always consistent with those obtained in mammals. In this context the main objective of the present study was to investigate the effects of goitrogenic compounds in the teleost fish, sea bream and analyze whether these compounds can depress TH production and determine how they influence different components of the thyroid axis in fish. Juvenile fish (~50 g BW) were treated for a period of 21 days with the goitrogens, MMI, PTU and thiourea (1mg/kg day through the food). Assessment of the impact of goitrogens on the central control of the thyroid cascade was assessed by histological investigation of thyroid follicles and thyroid stimulant hormone gene expression in the pituitary by qPCR, in addition to measurements of plasma thyroxine (T4) levels by radioimmunoassay. The effect of goitrogens on peripheral control was assessed by thyronine (T3) measurements in plasma and by determining deiodinase gene expression in the pituitary, liver and kidney. TH transport was also analysed by measuring transthyretin (TTR) plasma levels by Western blot and gene expression in liver with a specific quantitative PCR reaction. Only MMI significantly depressed TH production (p<0.05), especially T4. Histological appearance of the thyroid tissue in this group was indicative of increased thyroid follicle activity and was substantially different from control fish or those treated with PTU or thiourea. In MMI treated fish most of the thyroid follicles were collapsed and contained little colloid which was full of vacuoles and intracellular colloid droplets were evident in the thyrocytes. PTU treatment did not disrupt TH production, however also induced hyperplasia and hypertrophy of the thyrocytes, although it was less marked than that seen in MMI treatment. The relative expression of DI and DII in MMI treated fish was increased in the liver in parallel with the induced hypothyroidism. In contrast to the situation in the liver DI in the kidney is unresponsive to changes in the thyroid status in sea bream. MMI also decreased expression of the thyroid hormone receptor beta (TRβ) in the pituitary parallel to TH depletion, but no significant differences were found in the concentration of plasma TTR or hepatic gene expression (p> 0.05). These data demonstrate that in sea bream MMI seems to function in the same manner as reported in mammals, probably by inhibiting thyoperoxidases ability to activate iodine and transfer it to thyroglobulin. The alterations in deiodinase expression fits well with the general notion that in the sea bream in common with other teleosts peripheral deiodination is the primary control mechanism of thyroid function, independent of the hypothalamus-pituitary-thyroid axis.
Goitrogens são compostos naturais ou sintéticos que podem afectar o funcionamento da tiróide e inibir a produção das hormonas da tiróide. Methimazole (MMI), propylthiouracil (PTU) e thiourea, são utilizados no tratamento clínico do hipertiroidismo em humanos e mecanismo de acção destes compostos em mamíferos é relativamente bem conhecido. Em peixes estes compostos têm sido utilizados com o objectivo de induzir hipotiroidismo, assumindo que o sistema da tiróide trabalha da mesma forma. No entanto a acção destes compostos em peixes não tem sido suficientemente estudada e os efeitos observados muitas vezes diferem com os efeitos observados em mamíferos. Neste contexto, o objectivo do presente estudo foi investigar o efeito de compostos goitrogénicos em diferentes componentes do eixo da tiróide em sea bream, um peixe teleosteo, e analisar se estes compostos podem bloquear a produção das hormonas da tiróide. Juvenis (~50 g BW) foram tratados durante 21 dias com MMI, PTU e thiourea (1mg/kg dia – através da alimentação). Os níveis das hormonas da tiróide (T3 e T4) no plasma foram medidos por radioimunoensaio, as alterações no tecido da tiróide foram observadas e o nível de expressão de um grupo de genes envolvido na produção das hormonas da tiróide (TR,TSH,TTR e Deiodinases) foi quantificado por qPCR na pituitária, fígado e rim. Unicamente MMI diminuiu a produção das hormonas da tiróide significativamente (p<0,05), principalmente T4. O aspecto histológico do tecido da tiróide neste grupo foi indicativo de um aumento na actividade dos folículos, tendo sido drasticamente diferente dos do grupo controlo ou do grupo tratado com PTU ou thiourea. O tratamento com PTU não bloqueou a produção das hormonas, no entanto também desenvolveu tirócitos hiperplásticos e hipertrofiados, no entanto em menor intensidade do que MMI. A expressão relativa de DI e DII no tratamento com MMI foi aumentada no fígado ao mesmo tempo que o hipotiroidismo foi induzido, no entanto a expressão de DI no rim não foi alterada. MMI também diminuiu a expressão do receptor beta das hormonas da tiróide em paralelo à diminuição dos níveis das hormonas no plasma, mas não foram observadas diferenças significativas na concentração de TTR no plasma ou a sua expressão no fígado (p<0,05). Os resultados obtidos demonstram que em sea bream MMI parece actuar da mesma forma do que nos mamíferos, provavelmente pela inibição da capacidade das thyoperoxidases de activar o iodo a transferi-lo a tiroglobulína. A alteração na expressão das deiodinases esta de acordo com a ideia de que sea bream em comum com outros teleosteos o principal mecanismo de controlo da função da tiróide é a deiodinaçao periferal, independentemente do eixo hipotalamo-pituitaria-tiroide.

Thyroxine (T4), the main secretory hormone of the thyroid gland, is produced on thyroglobulin by thyroid peroxidase (TPO)/hydrogen peroxide/iodide system. The synthesis of T4 by TPO involves two independent steps: iodination of tyrosine and phenolic coupling of the resulting iodotyrosine residues. The prohormone T4 is then converted to its biologically active form T3 by a selenocysteine-containing iodothyronine deiodinase (ID-I), which is present in highest amounts in liver, kidney, thyroid and pituitary. The 5'-deiodination catalyzed by ID-I is a ping-pong, bisubstrate reaction in which the selenol (or selenolate) group of the enzyme (E-SeH or E-Se-) first reacts with thyroxine (T4) to form a selenenyl iodide (E-SeI) intermediate. Subsequent reaction of the selenenyl iodide with an as yet unidentified intracellular cofactor completes the catalytic cycle and regenerates the selenol. Although the deiodination reactions are essential for the function of thyroid gland, the activation of thyroid stimulating hormone (TSH) receptor by auto-antibodies leads to an overproduction of thyroid hormones. In addition, these antibodies stimulate ID-I and probably other deiodinases to produce relatively more amount of T3. Figure 1. Synthesis of thyroid hormones by heme-containing Thyroid Peroxidase(TPO)(Refer PDF File) As these antibodies are not under pituitary feedback control system, there is no negative influence on the thyroid activity and, therefore, the uncontrolled production of thyroid hormones leads to a condition called “hyperthyroidism”. Under these conditions, the overproduction of T4 and T3 can be controlled by specific inhibitors, which either block the thyroid hormone biosynthesis or reduce the conversion of T4 to T3. A unique class of such inhibitors is the thiourea drugs, methimazole (1, MMI), 6-n-propyl-2-thiouracil (3, PTU), and 6-methyl-2-thiouracil (5, MTU). Although these compounds are the most commonly employed drugs in the treatment of hyperthyroidism, the detailed mechanism of their action is still not clear. According to the initially proposed mechanism, these drugs may divert oxidized iodides away from thyroglobulin by forming stable electron donor-acceptor complexes with diiodine, which can effectively reduce the thyroid hormone biosynthesis. It has also been proposed that these drugs may block the thyroid hormone synthesis by coordinating to the metal center of thyroid peroxidase (TPO). After the discovery that the ID-I is responsible for the activation of thyroxine, it has been reported that PTU, but not MMI, reacts with the selenenyl iodide intermediate (E-SeI) of ID-I to form a selenenyl sulfide as a dead end product, thereby blocking the conversion of T4 to T3 during the monodeiodination reaction. The mechanism of anti-thyroid activity is further complicated by the fact that the gold-containing drugs such as gold thioglucose (GTG) inhibit the deiodinase activity by reacting with the selenol group of the native enzyme. Recently, the selenium analogues 2 (MSeI), 4 (PSeU) and 6 (MSeU) attracted considerable attention because these compounds are expected to be more nucleophilic than their sulfur analogues and the formation of an –Se–Se– bond may occur more readily than the formation of an –Se–S– bond with the ID-I enzyme. However, the data derived from the inhibition of TPO by selenium compounds show that these compounds may inhibit the TPO activity by a different mechanism. Therefore, further studies are required to understand the mechanism by which the selenium compounds exert their inhibitory action. Our initial attempts to isolate 2 were unsuccessful and the final stable compound in the synthesis was characterized to be the diselenide (8). In view of the current interest in anti-thyroid drugs and their mechanism, we extended our approach to the synthesis and biological activities of a number of sulfur and selenium derivatives bearing the methimazole pharmacophore. The thesis consists of five chapters. The first chapter gives a general introduction to thyroid hormone synthesis and anti-thyroid drugs. In this chapter, the biosynthesis of thyroid hormones, structure and function of heme peroxidases, activation of thyroid hormones by iodothyronine deiodinases are discussed. This chapter also gives a brief introduction to some common problems associated with the thyroid gland, with a particular emphasis on hyperthyroidism. The structure and activity of some commonly used anti-thyroid drugs and the role of selenium in thyroid are discussed. The literature references related to this work are provided at the end of the chapter. The second chapter deals with the synthesis and characterization of the selenium analogue (MSeI) of anti-thyroid drug methimazole and a series of organoselenium compounds bearing N-methylimidazole pharmacophore are described. The clinically employed anti-thyroid drug, methimazole (MMI), exists predominantly in its thione form, which is responsible for its anti-thyroidal activity. The selenium analogue MSeI, on the other hand, is not stable in air and spontaneously oxidizes to the corresponding diselenide (MSeIox). Experimental and theoretical studies on MSeI suggest that this compound exists in a zwitterionic form in which the selenium atom carries a large negative charge. The structure of MSeI was studied in solution by NMR spectroscopy and the 77Se NMR chemical shift shows a large upfield shift (-5 ppm) in the signal as compared to the true selones for which the signals normally appear in the downfield range (500-2500 ppm). This confirms that MSeI exists predominantly in its zwitterionic form in solution. Our theoretical studies show that the formation of the diselenide (MSeIox) from selenol tautomer is energetically more favored than the formation of the disulfide (MMIox) from the thiol tautomer of MMI. This study also shows that the replacement of the N−H group in MSeI by an N-methyl or N-benzyl substituent does not affect the nature of C−Se bond. In the third chapter, the inhibition of lactoperoxidase-catalyzed oxidation of ABTS by anti-thyroid drugs and related derivatives is described. The commonly used anti-thyroid agent methemazole (MMI) inhibits the lactoperoxidase (LPO) with an IC50 value of 7.0 µM which is much lower than that of the other two anti-thyroid drugs, PTU and MTU. The selenium analogue of methimazole (MSeI) also inhibits LPO with an IC50 value of 16.4 µM, which is about 4-5 times lower than that of PTU and MTU. In contrast to thiones and selones, the S- and Se-protected compounds do not show any noticeable inhibition under identical experimental conditions. While the inhibition of LPO by MMI cannot be reversed by increasing the hydrogen peroxide concentration, the inhibition by MSeI can be completely reversed by increasing the peroxide concentration. Some of the selenium compounds in the present study show interesting anti-oxidant activity in addition to their inhibition propertities. In the presence of glutathione (GSH), MSeI constitutes a redox cycle involving a catalytic reduction of H2O2 and thereby mimics the glutathione peroxidase (GPx) activity in vitro. These studies reveal that the degradation of the intracellular H2O2 by the selenium analogues of anti-thyroid drugs may be beneficial to the thyroid gland as these compounds may act as antioxidants and protect thyroid cells from oxidative damage. Because the drugs with an action essentially on H2O2 can reversibly inhibit thyroid peroxidase, such drugs with a more controlled action could be of great importance in the treatment of hyperthyroidism. Figure 2. (A) Concentration-inhibition curves for the inhibition of LPO-catalyzed oxidation of ABTS by MMI and MSeI at pH 7.0 and 30 °C. (B) Plot of initial rates (vo) for the LPO-catalyzed oxidation of ABTS vs concentration of H2O2. (a) Control activity, (b) 40 µM of MSeI, (c) 40 µM of MSeIox, (d) 80 µM of PTU, (e) 80 µM of MTU, (f) 40 µM of MMI. The incubation mixture contained 6.5 nM LPO, 1.4 mM ABTS, 0.067 M phosphatebuffer(pH7).(Refer PDF File) The fourth chapter describes the inhibition of lactoperoxidase (LPO)-catalyzed iodination of L-tyrosine by anti-thyroid drug methimazole (MMI) and its selenium analogue (MSeI). These inhibition studies show that MSeI inhibits LPO with an IC50 value of 12.4 µM, which is higher than that of MMI (5.2 µM). The effect of hydrogen peroxide on the inhibition of LPO by MMI and MSeI is also discussed. These studies also reveal that the inhibition of LPO-catalyzed iodination by MSeI can be completely reversed by increasing the peroxide concentration. On the other hand, the inhibition by MMI cannot be reversed by increasing the concentration of the peroxide. To under stand the nature of compounds formed in the reactions between anti-thyroid drugs and iodine, the reactions of MSeI with molecular iodine is described. MSeI reacts with I2 to produce novel ionic diselenides, and the nature of the species formed in this reaction appears to be solvent dependent. The formation of ionic species (mono and dications) in the reaction is confirmed by UV-Vis, FT-IR and FT-Raman spectroscopic investigations and single crystal x-ray studies. The major conclusion drawn from this study is that MSeI reacts with iodine, even in its oxidized form, to form ionic diselenides containing iodide or polyiodide anions, which might be possible intermediates in the inhibition of thyroid hormones. Dication X-ray crystal structure of the monocation X-ray crystal structure of the dication In the fifth chapter, the synthesis and characterization of several thiones and selones having N,N-disubstituted imidazole moiety are described. Experimental and theoretical studies were performed on a number of selones, which suggest that these compounds exist as zwitterions in which the selenium atom carries a large negative charge. The structures of selones were studied in solution by NMR spectroscopy and the 77Se NMR chemical shifts for the selones show large upfield shifts in the signals, confirming the zwitterionic structure of the selones in solution. The thermal isomerization of some S- and Se-substituted methyl and benzyl imidazole derivatives to produce the thermodynamically more stable N-substituted derivatives is described. A structure–activity correlation was attempted on the inhibition of LPO-catalyzed oxidation and iodination reactions by several thiouracil compounds, which indicates that the presence of an n-propyl group in PTU is important for an efficient inhibition. In contrast to the S- and Se-substituted derivatives, the selones produced by thermal isomerization exhibited efficient inhibition, indicating the importance of reactive selone (zwitterionic) moiety in the inhibition. The inhibition data on another well-known anti-thyroid agent carbimazole (CBZ) support the assumption that CBZ acts as a prodrug, requiring a conversion to methimazole (MMI) for its inhibitory action on thyroid peroxidase. (Refer pdf file/original thesis)