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Thesis (Ph.D.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 210 pages. Includes Vita. Includes bibliographical references.

With the increasing demand for assisted reproduction, more knowledge and understanding towards health requirements of oocytes and their inner workings are required. With current IVF success rates of approximately 40%, oocyte and embryo culture conditions in vitro can be improved by first understanding the finer details of oocyte function. As such, there is a need to better understand the mechanisms through which oocytes can acquire certain nutrients. This thesis focuses on the amino acid serine, which has been shown to improve outcome in developing embryos and also plays a variety of roles in the body that may carry over to oocyte health as well. Using radiolabeled [3H] serine, we measured uptake of serine as a function of time throughout growth and meiotic maturation in mouse oocytes. Serine transport appeared in oocytes during growth and became absent in mature eggs. With a competition assay using substrates diagnostic for several different amino acid transporter systems and culture with and without sodium in the external medium, I identified Na+-dependent SNAT7 of the System A/N (SLC38) family to be the most likely transporter in oocytes. Quantitative RT-PCR was consistent with this result. Transporter activity is also not activated by progression of meiotic maturation, as indicated by unperturbed transport when dbcAMP was provided to maintain meiotic arrest. However, a biological regulator of arrest, NPPC, resulted in enhanced transport activity in vitro. This may be due to signalling mechanisms of the NPPC pathway affecting regulation of serine uptake, which presents a direction for future research.

Protozoários do gênero Leishmania são parasitas digenéticos, com uma fase no tubo digestório de um hospedeiro invertebrado (promastigota), e uma fase parasita intracelular de macrófagos (amastigotas). Estudar a demanda de L-arginina no parasita é interessante, uma vez que o aminoácido é indispensável para a sobrevida do parasita e, ao mesmo tempo, serve de substrato para a produção de óxido nítrico, principal composto microbicida dos macrófagos. O objetivo deste trabalho foi caracterizar o transporte de arginina em Leishmania (Leishmania) amazonensis do ponto de vista fisiológico e caracterizar o gene que codifica o transportador do aminoácido, bem como a regulação da sua expressão em resposta a diferentes condições biológicas. Para medir o influxo de L-arginina em fagolisossomos, utilizamos macrófagos J774 infectados com L. (L.) amazonensis e desenvolvemos uma metodologia com citometria de fluxo com sorting para a purificação da organela. Validamos microscopicamente a presença do parasita na organela por sua fluorescência, e avaliamos a integridade da membrana externa dessa com marcador de pH ácido. Paralelamente, o gene que codifica o transportador de arginina do parasita foi caracterizado. Foram encontradas duas cópias em tandem que produzem dois transcritos (5.1AAP3 e 4.7AAP3), cujas regiões 5\'UTR e 3\'UTR são diferentes. Por meio de PCR quantitativo em tempo real, avaliamos a expressão desses transcritos e verificamos que 5.1AAP3 é mais expressa ao longo do desenvolvimento do parasita, com um máximo em fase estacionária. A determinação da meia-vida dos mRNA das duas cópias indicou uma duração de 32,6±5,0min para o mRNA de 4.7AAP3, enquanto que o de 5.1AAP3 não apresentou decaimento até 180min do estudo, evidenciando que a estabilidade maior pode ser a razão de sua maior abundância. A submissão de parasitas à privação de arginina levou a aumento na tomada do aminoácido concomitante ao aumento do transcrito 5.1AAP3. Mutantes nulos de arginase submetidos à privação de arginina respondem com uma taxa de incorporação mais baixa em relação aos parasitas selvagens, e mantém a resposta à privação mesmo com os parasitas em fase estacionária, diferente do observado nos parasitas selvagens. Esse conjunto de resultados nos levou a sugerir que a expressão do transportador pode ser regulada pela estabilidade do mRNA, e que o pool de arginina interno ao parasita pode controlar, num mecanismo de retroalimentação negativo, a expressão de seu transportador. / Protozoan of genus Leishmania are digenetic parasites that present a stage in the life in insect gut (promastigotes) and an intracellular phase (amastigotes) inside vertebrate host macrophages. The study of L-arginine influx consists in an interesting matter, since the amino acid is used on NO production pathway (the main macrophage microbial pathway) but are also important for parasites survival. The aim of this work was to perform a genetic and physiological characterization of the arginine transport in Leishmania (Leishmania) amazonensis. To verify how does the arginine uptake occurs in the phagolisosomes, we used J774 macrophages infected with L. (L.) amazonensis to establish a flow cytometry sorting protocol to purify the organelle. Microscopic validation of organelle integrity was achieved by acidic pH marker treatment and detection of fluorescent parasites. The arginine transporter coding gene was characterized. We found two copies in tandem that produces two transcripts, named 5.1AAP3 and 4.7AAP3, with distinct 5\'UTR and 3\'UTR. By quantitative real time PCR we found that 5.1AAP3 mRNA expression varies along parasite development. This copy was, also, more abundant than 4.7AAP3 mRNA. This last mRNA showed a half-life of 32.6±5.0 min, while the 5.1AAP3 mRNA did not decay until 180min. As response to arginine starvation, wild type parasites increase the uptake of arginine, as well as the abundance of 5.1AAP3 mRNA. Arginase null parasites starvation responses showed lower arginine uptake rates compared to wild type responses. Unlike wild type, the null mutants also respond to starvation in stationary phase. This data set allow us to propose that arginine internal pool can downregulate its transporter expression in a feed-back mechanism.

Protozoários do gênero Leishmania são parasitas digenéticos, com uma fase no tubo digestório de um hospedeiro invertebrado (promastigota), e uma fase parasita intracelular de macrófagos (amastigotas). Estudar a demanda de L-arginina no parasita é interessante, uma vez que o aminoácido é indispensável para a sobrevida do parasita e, ao mesmo tempo, serve de substrato para a produção de óxido nítrico, principal composto microbicida dos macrófagos. O objetivo deste trabalho foi caracterizar o transporte de arginina em Leishmania (Leishmania) amazonensis do ponto de vista fisiológico e caracterizar o gene que codifica o transportador do aminoácido, bem como a regulação da sua expressão em resposta a diferentes condições biológicas. Para medir o influxo de L-arginina em fagolisossomos, utilizamos macrófagos J774 infectados com L. (L.) amazonensis e desenvolvemos uma metodologia com citometria de fluxo com sorting para a purificação da organela. Validamos microscopicamente a presença do parasita na organela por sua fluorescência, e avaliamos a integridade da membrana externa dessa com marcador de pH ácido. Paralelamente, o gene que codifica o transportador de arginina do parasita foi caracterizado. Foram encontradas duas cópias em tandem que produzem dois transcritos (5.1AAP3 e 4.7AAP3), cujas regiões 5\'UTR e 3\'UTR são diferentes. Por meio de PCR quantitativo em tempo real, avaliamos a expressão desses transcritos e verificamos que 5.1AAP3 é mais expressa ao longo do desenvolvimento do parasita, com um máximo em fase estacionária. A determinação da meia-vida dos mRNA das duas cópias indicou uma duração de 32,6±5,0min para o mRNA de 4.7AAP3, enquanto que o de 5.1AAP3 não apresentou decaimento até 180min do estudo, evidenciando que a estabilidade maior pode ser a razão de sua maior abundância. A submissão de parasitas à privação de arginina levou a aumento na tomada do aminoácido concomitante ao aumento do transcrito 5.1AAP3. Mutantes nulos de arginase submetidos à privação de arginina respondem com uma taxa de incorporação mais baixa em relação aos parasitas selvagens, e mantém a resposta à privação mesmo com os parasitas em fase estacionária, diferente do observado nos parasitas selvagens. Esse conjunto de resultados nos levou a sugerir que a expressão do transportador pode ser regulada pela estabilidade do mRNA, e que o pool de arginina interno ao parasita pode controlar, num mecanismo de retroalimentação negativo, a expressão de seu transportador. / Protozoan of genus Leishmania are digenetic parasites that present a stage in the life in insect gut (promastigotes) and an intracellular phase (amastigotes) inside vertebrate host macrophages. The study of L-arginine influx consists in an interesting matter, since the amino acid is used on NO production pathway (the main macrophage microbial pathway) but are also important for parasites survival. The aim of this work was to perform a genetic and physiological characterization of the arginine transport in Leishmania (Leishmania) amazonensis. To verify how does the arginine uptake occurs in the phagolisosomes, we used J774 macrophages infected with L. (L.) amazonensis to establish a flow cytometry sorting protocol to purify the organelle. Microscopic validation of organelle integrity was achieved by acidic pH marker treatment and detection of fluorescent parasites. The arginine transporter coding gene was characterized. We found two copies in tandem that produces two transcripts, named 5.1AAP3 and 4.7AAP3, with distinct 5\'UTR and 3\'UTR. By quantitative real time PCR we found that 5.1AAP3 mRNA expression varies along parasite development. This copy was, also, more abundant than 4.7AAP3 mRNA. This last mRNA showed a half-life of 32.6±5.0 min, while the 5.1AAP3 mRNA did not decay until 180min. As response to arginine starvation, wild type parasites increase the uptake of arginine, as well as the abundance of 5.1AAP3 mRNA. Arginase null parasites starvation responses showed lower arginine uptake rates compared to wild type responses. Unlike wild type, the null mutants also respond to starvation in stationary phase. This data set allow us to propose that arginine internal pool can downregulate its transporter expression in a feed-back mechanism.

Pre-eclampsia (PE) is a serious disease affecting approximately 5% of pregnancies per annum. The disease etiology is complex but its origin lies in abnormal placental development and function. PE is associated with inflammation, increased nitrative stress and abnormal renewal of syncytiotrophoblast (STB), the transporting epithelium of the placenta. STB is renewed by cytotrophoblasts (CTBs) that proliferate, differentiate and fuse with STB and this is balanced by apoptosis. The amino acid taurine facilitates proliferation, differentiation and apoptosis in non-placental tissues. Taurine is also cytoprotective, protecting cells from damage by inflammatory cytokines. Taurine is transported from maternal blood into STB by the amino acid transporter TauT. In isolated STB membranes, TauT activity is inhibited by agents that nitrate tyrosine residues. This thesis tested the hypothesis that STB TauT activity is down-regulated in PE due to post-translational modification of TauT through tyrosine nitration which lowers intracellular taurine and contributes to altered STB renewal. Placentas were collected from normal pregnancy (NP) and PE (blood pressure >140/90mmHg after 20 weeks gestation in previously normotensive women plus proteinuria >300 mg/L in a 24-hour collection). STB TauT activity, measured as Na+-dependent uptake of 3H-taurine into placental villous fragments, was significantly lower in PE (n=24) compared to NP (n=44). Western blotting of membrane enriched homogenates showed that TauT protein expression (normalised to β-actin) was significantly higher in placentas from PE (n=8) compared to NP (n=9). The presence of nitrotyrosine residues (marker of nitrative stress) in placentas of women with PE and NP was assessed by immunohistochemistry (IHC). The intensity of STB nitrotyrosine staining was greater in PE placentas that had reduced TauT activity (n=8) than in NP (n=7). To determine the effect of nitrative stress on TauT activity and STB renewal, placental villous explants from NP were cultured (7 days; n=6) and treated with SIN-1 (1mM; days 5,6) to induce nitrative stress. STB nitrotyrosine (IHC) and TauT activity (3H-taurine uptake) was determined on day 7 and STB renewal was assessed by IHC for apoptosis (M30), proliferation (dual staining for Ki67 and the CTB marker E-cadherin) and STB integrity (cytokeratin 7). SIN-1 increased STB nitrotyrosine staining intensity compared to controls, confirming induction of nitrative stress. SIN-1 reduced STB TauT activity, increased apoptosis, reduced CTB proliferation and altered STB regeneration compared to control. To determine the effect of reducing intracellular taurine on STB renewal, villous explants were cultured for 7 days with 2.5mM β-alanine to competitively inhibit taurine uptake (n=6). At day 7, intracellular taurine, measured as the steady-state accumulation of 3H-taurine, was 15% of normal. STB turnover was assessed at day 7 as described above. β-alanine significantly increased apoptosis and altered STB regeneration compared to controls. Following statistical analysis all p <0.05.In conclusion, STB TauT activity was lower, and protein expression higher, in PE compared to NP. STB nitrotyrosine was elevated in PE and nitrative stress inhibited STB TauT activity and disrupted STB renewal in vitro. Reducing intracellular taurine also disrupted STB renewal in vitro. Overall the data support the hypothesis that post-translational modification of TauT by nitration inhibits TauT activity in PE. This reduces intracellular taurine which contributes to abnormal renewal of STB. Further work is needed (a) to confirm that TauT is nitrated in PE and that reduced STB TauT activity lowers intracellular taurine and reduces taurine delivery to the fetus and (b) to determine the mechanism/s by which taurine regulates CTB apoptosis and facilitates renewal of STB.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 128-140).

Thesis (Ph.D. in Microbiology) -- University of Colorado at Denver and Health Sciences Center, 2005. / Typescript. Includes bibliographical references (leaves 201-223).