MARCIA AUGUSTA DA SILVA
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Artigo IPEN-doc 22433 Cytotogenic and dosimetric effects of sup(131)I in patients with differentiated thyroid carcinoma: comparison between stimulation with rhTSH and thyroid hormone withdrawal treatments2016 - SILVA, MARCIA A. da; VALGODE, FLAVIA G.S.; GONZALEZ, JULIA A.; YORIYAZ, HELIO; GUIMARAES, MARIA I.C.C.; RIBELA, MARIA T.C.P.; BUCHPIGUEL, CARLOS A.; BARTOLINI, PAOLO; OKAZAKI, KAYOA study directed to the cytogenetic and dosimetric aspects of radionuclides of medical interest is very valuable, both for an accurate evaluation of the dose received by the patients, and consequently of the genetic damage, and for the optimization of therapeutic strategies. Cytogenetic and dosimetric effects of 131I in lymphocytes of thyroidectomized differentiated thyroid cancer (DTC) patients were evaluated through chromosome aberration (CA) technique: Euthyroid patients submitted to recombinant human thyroid-stimulating hormone (rhTSH) therapy (group A) were compared with hypothyroid patients left without levothyroxine treatment (group B). CA analysis was carried out prior to and 24 h, 1 week, 1 month and 1 year after radioiodine administration (4995–7030 MBq) in both groups. An activity–response curve of 131I (0.074–0.740 MBq/mL) was elaborated, comparing dicentric chromosomes in vivo and in vitro in order to estimate the absorbed dose through Monte Carlo simulations. In general, radioiodine therapy induced a higher total CA rate in hypothyroid patients as compared to euthyroid patients. The frequencies of dicentrics obtained in DTC patients 24 h after treatment were equivalent to those induced in vitro (0.2903 ± 0.1005 MBq/mL in group A and 0.2391 ± 0.1019 MBq/mL in group B), corresponding to absorbed doses of 0.65 ± 0.23 Gy and 0.53 ± 0.23 Gy, respectively. The effect on lymphocytes of internal radiation induced by 131I therapy is minimal when based on the frequencies of CA 1 year after the treatment, maintaining a higher quality of life for DTC patients receiving rhTSHaided therapy.Artigo IPEN-doc 07134 Evaluation of the effect of 90Sr β-radiation on human blood cells by chromosome aberration and single cell gel electrophoresis (comet assay) analysis2001 - OLIVEIRA, E.M.; SUZUKI, M.F.; NASCIMENTO, P.A.; SILVA, M.A.; OKAZAKI, K.Among various environmental genotoxins, ionizing radiation has received special attention because of its mutagenic, carcinogenic and teratogenic potential. In this context and considering the scarcity of literature data, the objective of the present study was to evaluate the effect of 90Sr β-radiation on human cells. Blood cells from five healthy donors were irradiated in vitro with doses of 0.2-5.0 Gy from a 90Sr source (0.2 Gy/min) and processed for chromosome aberration analysis and for comet assay. The cytogenetic results showed that the most frequently found aberration types were acentric fragments, double minutes and dicentrics. The α and β coefficients of the linear-quadratic model, that best fitted the data obtained, showed that 90Sr β-radiation was less efficient in inducing chromosome aberrations than other types of low linear energy transfer (LET) radiation such as 3H β-particles, 60Co γ-rays, 137Cs and 192Ir and X-rays. Apparently, 90Sr β-radiation in the dose range investigated had no effect on the modal chromosome number of irradiated cells or on cell cycle kinetics. Concerning the comet assay, there was an increase in DNA migration as a function of radiation dose as evaluated by an image analysis system (tail moment) or by visual classification (DNA damage). The dose-response relation adequately fitted the non-linear regression model. In contrast to the cytogenetic data, 90Sr β-radiation induced more DNA damage than 60Co γ-radiation when the material was analyzed immediately after exposures. A possible influence of selective death of cells damaged by radiation was suggested.Artigo IPEN-doc 13173 Evaluation of the cytogenetic effects of 131I preceded by recombinant human thyrotropin (rhTSH) in peripheral lymphocytes of Wistar rats2008 - SILVA, MARCIA A. da; GUIMARAES, MARIA I.C.C.; YORIYAZ, HELIO; RIBELA, MARIA T.C.P.; BUCHPIGUEL, CARLOS A.; BARTOLINI, PAOLO; OKAZAKI, KAYOThe present study was carried out to investigate the cytogenetic effects of therapeutic exposure to radioiodine preceded by rhTSH in an animal model. Three groups of Wistar rats (n = 6) were used: one group was treated only with 131I (11.1 MBq/animal); the other two groups received rhTSH (1.2 μg/rat of either Thyrogen or rhTSH-IPEN, respectively) 24 h before administration of radioiodine. The percentage of lymphocytes with chromosome aberrations and the average number of aberrations and of dicentrics per cell were determined on blood samples collected 24 h, 7 and 30 days after administration of 131I. The data show that the treatment with radioiodine alone or associated with rhTSH resulted in a greater quantity of chromosome alterations in relation to basal values after 24 h, with a gradual decline after 7 and 30 days of treatment. An increase in chromosome alterations was also seen after rhTSH treatment alone. Neither of the treatments, i.e., with 131I alone or associated with hormone, resulted in an aneugenic effect or influenced the kinetics of cellular proliferation in rat blood lymphocytes. There was no significant difference between the cytogenetic effects of Thyrogen and rhTSH-IPEN treatment. These data suggest that the treatment with radioiodine, associated or not with rhTSH, affects to a limited extent a relatively small number of cells although the occurrence of late stochastic effects could not be discarded.