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The fluoride anion plays an important role in dental health and as a result is added to drinking water at low concentrations. If the concentration of fluoride is too high however, skeletal fluorosis can occur. Because of this, there has been significant interest in the development of water compatible anion sensors that can sense fluoride at the ppm level. This is made difficult by the high hydration enthalpy of fluoride (ΔH0 = -504 KJ/mol) which significantly lowers the reactivity of this anion in water. For this reason it has become the goal of the Gabbaï group, as well as other research groups to develop fluoride sensing small molecules. Such molecules should possess sufficient Lewis acidity to overcome the hydration enthalpy of the fluoride anion. A significant amount of research has been conducted on triarylboranes containing cationic moieties such as ammonium, phosphonium, and sulfonium groups. This thesis will describe additional examples of such species, including a series of ammonium boranes of the general formula [p-(Mes2B)C6H4(NMe2R)]+. As indicated by anion complexation studies, the R group present in these molecules has a notable effect on the anion affinity of the somewhat distant boron center. Another component of this thesis deals with the chemistry of newly synthesized stiboranes that are also decorated by peripheral ammonium groups. As observed for the ammonium boranes mentioned above, the ammonium groups present in these stiboranes drives anion capture, leading to zwitterionic ammonium antimonite formation.

Univ., Diss.--Würzburg, 1998.

Thesis (Ph. D. in Engineering)--University of California, Berkeley, Sept. 1961. / Bibliography: l. 74-78.

University, Diss., 2006--Würzburg.

Orientador: Doris Hissako Sumida / Banca: Roberta Okamoto / Banca: Sérgio Eduardo de Andrade Perez / Resumo: O flúor é um elemento traço essencial para a manuten ção da saúde óssea, devido à capacidade de estimular a proliferação osteoblástica, levando ao aumento da formação óssea. No entanto, a ingestão excessiva de fluoreto de sódio pode prejudicar o metabolismo dos carboidratos, promovendo hiperglicemia, resistê ncia à insulina e alterações no sinal insulínico. Dessa forma, este estudo teve como objetivo avaliar o efeito do tratamento crônico com NaF no metabolismo ósseo, na sinalização insulínica e nas concentrações plasmáticas de glicose, insulina, flúor, TNF - α e osteocalcina em ratas ovariectomizadas. Trinta e seis ratas Wistar ovariectomizadas foram distribuídas aleatoriamente em dois grupos: OVX - C, como grupo controle, e grupo OVX - F, que foi submetido ao tratamento com NaF (50 mg F/L) na água de beber durante 42 dias. Foram determinadas as concentrações plasmáticas de glicose e insulina, seguido pelo cálculo do HOMA - IR. A fosforilação em serina da Akt foi avaliada pelo método de Western blotting. As tíbias direita e esquerda foram coletadas para análises imuno - histoquímica e histomorfométrica. Os resultados do presente estudo demonstraram que o tratamento crónico com NaF promoveu resistência à insulina, diminuição do sinal insulínico, aumento das concentrações plasmáticas de insulina, flúor, osteocalcina e TNF - α ; diminuição da área óssea trabecular da tíbia e alterações nos marcadores do metabolismo ósseo em ratas ovariectomizadas. Esses resultados sugerem cautela no uso de NaF para o tratamento da osteoporose, especialmente em mulheres na pós-menopausa / Abstract: Fluoride is an essential trace element for the maintenance of bone health due its capacity of stimulating the proliferation and osteoblastic activity that can lead to increase bone formation. However, excessive sodium fluoride intake can impair carbohydrate metabolism, promoting hyperglycemia, insulin resistance and change in insulin signal. Thus, this study aimed to evaluate the effect of chronic treatment with NaF in bone metabolism; insulin signaling; plasma concentrations of glucose, insulin, TNF-α, osteocalcin and fluoride in ovariectomized rats. Thirty six ovariectomized Wistar rats were randomly distributed into two groups: OVX-C, as control group, and OVX-F group, undergoing treatment with NaF (50mg F/L) in drinking water for 42 days. Plasma concentration of glucose and insulin were assessed, followed by homeostasis model assessment of insulin resistance (HOMA-IR). The Akt serine phosphorylation was evaluated by western blotting. The right and left tibias were collected for immunohistochemical and histomorphometric analysis, respectively. The chronic treatment with NaF promoted insulin resistance; decreased insulin signal; increase in the plasma concentration of insulin, fluoride, osteocalcin and TNF-α; decreased trabecular bone area of the tibia and changes in bone metabolism markers in ovariectomized rats. These results suggest caution in the use of NaF for the treatment of osteoporosis especially in postmenopausal woman / Mestre

A fluorose dentÃria à uma anomalia causada por ingestÃo excessiva de flÃor durante o perÃodo de formaÃÃo e desenvolvimento dos dentes, o que provoca o aparecimento de manchas brancas opacas no esmalte dentÃrio. Um estudo transversal de prevalÃncia de fluorose dentÃria e cÃrie foi realizado, em escolares na faixa etÃria de 10 a 14 anos, na comunidade rural de Rafael Arruda, municÃpio de Sobral no Estado do CearÃ, nordeste do Brasil. Nesta localidade, hà mais de dez anos, foi identificada a ocorrÃncia natural de altos teores de flÃor na Ãgua de consumo provavelmente devido a existÃncia de jazidas de fluorita no subsolo, contaminando os lenÃÃis freÃticos. O resultado da anÃlise da concentraÃÃo de flÃor na Ãgua das principais fontes revelou teores variando de 0,34 à 3,6 ppm, cerca de cinco vezes o teor considerado Ãtimo para o consumo humano, muitos dos quais ultrapassavam o limite recomendado que à de 1 ppm de flÃor. Foram submetidos ao exame clÃnico bucal 324 escolares, seguido de uma entrevista, buscando informaÃÃes relacionadas aos fatores que afetam a prevalÃncia e gravidade da fluorose dentÃria. Os Ãndices epidemiolÃgicos utilizados para fluorose dentÃria foram o Ãndice Dean e o Ãndice de Fluorose DentÃria da Comunidade, e para cÃrie o Ãndice CPO-D. Foi realizada uma anÃlise univariada entre a variÃvel dependente (F|uorose dentÃria) e as fatores predisponentes a esta, atravÃs do teste exato de Fischer. Entre as crianÃas examinadas 89,5% apresentaram algum grau de fluorose dentÃria, sendo 49,3% delas atingidas nas formas moderada e grave da intoxicaÃÃo, onde a forma mais prevalente foi a moderada (27,4%). NÃo houve estatisticamente diferenÃa significativa entre sexo e gravidade da fluorose. O Ãndice ComunitÃrio de Fluorose (CFI) encontrado foi de 2,3 correspondendo a um quadro grave, onde recomenda-se a desfluoretaÃÃo da Ãgua e caracteriza-se o problema como importante sob o ponto de vista da saÃde pÃblica. A prevalÃncia de cÃrie ocorreu em 88% da populaÃÃo, e o CPO-D mÃdio encontrado foi de 2,9, refletindo um padrÃo de severidade moderada segundo a OrganizaÃÃo Mundial da SaÃde. A evoluÃÃo dos componentes do CPO-D apresentou carÃter crescente com a idade e em relaÃÃo à necessidade de tratamento, a idade de 14 anos revelou uma experiÃncia presente de cÃrie da ordem de 30%. A fluorose dentÃria, constitui-se portanto, num problema de saÃde pÃblica para esta localidade que continua a consumir altos teores de flÃor na Ãgua, expondo-se diariamente ao risco de desenvolvimento de quadros de fluorose dentÃria, nos seus mais variados graus. A ingestÃo de altos teores de flÃor foi prejudicial causando fluorose dentÃria, mas nÃo encontramos benefÃcios adicionais na prevenÃÃo da cÃrie. Embora os resultados demonstrem uma prevalÃncia moderada de cÃrie, nÃo foi verificada associaÃÃo entre sua ausÃncia e a ocorrÃncia da fluorose.

Orientador: Livia Maria Andaló Tenuta. / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba. / Made available in DSpace on 2018-08-20T01:44:17Z (GMT). No. of bitstreams: 1 Silva_AmandaFalcaoda_M.pdf: 1498543 bytes, checksum: 27e089825c6e3d6a738cf8f3567dfa89 (MD5) Previous issue date: 2012 / Resumo: Dentifrícios fluoretados tem sido considerados responsáveis pelo declínio de cárie ocorrido mundialmente, entretanto, são também considerados fatores de risco para fluorose dental. Todavia, não tem sido encontrada correlação entre a dose de ingestão de fluoreto (F) pelo dentifrício, na idade de risco para o desenvolvimento de fluorose e sua posterior prevalência. Uma das razões para esse achado é que a concentração total de F no dentifrício e não aquela biodisponível (fração solúvel que é absorvida) tem sido considerada no cálculo da dose de ingestão. Nesse contexto, dentifrícios fluoretados contendo carbonato de cálcio como abrasivo apresentam parte do F total indisponível para ser absorvido, ou seja, na forma insolúvel, que sofre aumento em função do tempo...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: Fluoride toothpastes are considered responsible for caries decline worldwide but they are also considered as risk factors for dental fluorosis. Nonetheless, there has been no correlation between fluoride (F) intake from toothpaste in the age of risk for developing fluorosis and its subsequent prevalence. One reason for this finding is that the total F concentration in toothpastes and not that bioavailable (soluble fraction which is absorbed) has been considered in calculation of the F dose ingested...Note: The complete abstract is available with the full electronic document / Mestrado / Cariologia / Mestre em Odontologia

High F- groundwaters occur in various parts of South Africa, namely, the larger part of the Karoo, Limpopo, North West and Northern Cape Provinces. The use of these waters for drinking purposes on continual basis can lead to fluorosis. Fluorosis is a debilitating disease caused by drinking water with F- concentrations higher than ca. 1 mg.L-1. The disease is characterized by mottled teeth in dental fluorosis and brittle bones in severe skeletal fluorosis. Solution to this problem involves the implementation of a method for F- removal from water. Defluoridation has become a widely practiced process worldwide due to the problem of fluorosis caused by the presence of F- in drinking waters. Methods such as adsorption, precipitation, ion exchange and membrane processes have been employed for F- removal. Adsorption techniques, in particular using activated alumina have proven successful in removing F- from water. However, this method can not always be used in rural areas because of high costs and technical requirements. In this study, locally available clays were studied as potential substrates for F- removal from water. The first part of the study focused on the explanation of mechanisms and the development of an adsorption model. The exchange of OH- by F- in the clay structure is the principal mechanism that takes place during adsorption. The change in pH during this exchange process was studied to support and verify the fluoride-hydroxide exchange mechanism. In the second part of the study, locally available South African clays were studied as possible adsorbents for F- removal from water. Clays containing aluminium and iron oxide surfaces proved to be useful substrates for F- adsorption. The adsorption of F- onto clay samples was found to be pH dependent. Maximum adsorption was achieved at pH 5 for aluminium oxide type sorbents and pH 4 for iron oxides types such as goethite. The effect of physical and chemical pretreatment improved the adsorption capacity of some clays. Coating clay samples with aluminium and iron oxides enhanced the adsorption capacity of clays. The last part of the study involves the development of a cost-effective and quick way to assess the performance of clays as adsorbents for F- removal using laboratory scale defluoridation columns. / Prof. P.P. Coetzee

Gemcitabine (dFdC) is an effective chemotherapeutic nucleoside analogue for treatment of cancers and solid tumors. Gemcitabine’s chemotherapeutic effect is limited by its rapid intracellular deamination by cytidine deaminase into the inactive uracil derivative. Herein, I designed and synthesized two sets of gemcitabine analogues: i) a 4-N-alkyl gemcitabine analogue containing a β-keto sulfonate moiety, and ii) clickable analogues possessing silicon-fluoride acceptor building blocks. Both of these sets of analogues undergo efficient fluorination, including fluorination protocols compatible with 18F labeling. The synthesis of the 4-N-alkyl gemcitabine analogue bearing β-keto sulfonate moiety began with reaction of 4-N-tosylgemcitabine with 1-amino-10-undecene, followed by a series of oxidation and sulfonation steps which yielded the β-keto sulfonate analogues. The coupling of gemcitabine with carboxylic acids using peptide coupling conditions afforded 4-N-alkanoyl analogues with a terminal alkyne or azido moiety. Click reaction of these 4-N-alkanoyl analogues with dialkylsilyl building blocks gave 4-N-alkanoylsilanegemcitabine analogue. Reaction of 4-N-tosylgemcitabine with vii functionalized azidoalkyl amines provided 4-N-alkylgemcitabine with a terminal azido group. Coupling of the latter with dialkylsilyl building block provided 4-N-alkylsilanegemcitabine. Fluorination of 4-N-alkyl gemcitabine analogues with β-keto sulfonate moieties and of the trisubstituted silane derivatives with KF and 18-Crown-6 (CH3CN/75°C/0.5-1h), gave the corresponding fluorinated 4-N-alkyl and alkanoyl gemcitabine analogues under conditions that are compatible with protocols for positron emission tomography (PET) 18F labeling. The [18F] 4-N-alkyl and alkanoyl silane gemcitabine analogues were successfully synthesized on microscale and macroscale radiochemical protocols. The biodistribution of [18F] 4-N-alkyl gemcitabine analogue was analyzed via PET imaging. The cytotoxicity activity of the silane gemcitabine analogues were studied in cancer L1210 and HEK293 cell lines and their cellular uptake were investigated using HPLC analysis and fluorescence microscopy. Reduction of ribono-1,4-lactones and gulono-1,4-lactone as well as ribono-1,5-lactone and glucono-1,5-lactones with LTBH (1.2 equiv.) in CH2Cl2 at 0 °C for 30 min provided the corresponding pentose or hexose hemiacetals in chemoselective fashion and in high yields. Commonly used in carbohydrate chemistry protecting groups such as trityl, benzyl, silyl, acetals and to some extent acyls are compatible with this reduction.