Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 94-103.

Orientador: Pedro Luis da Costa Aguiar Alves / Coorientador: Alcebíades Rebouças São José / Banca: Silvano Bianco / banca: Tiago Pereira Salgado / Resumo: Panicum maximun está entre as plantas daninhas mais importantes nas culturas tropicais, justificando plenamente a necessidade de controlá-la, o que é feito basicamente com o emprego de herbicidas. Diante disso, objetivou-se avaliar o efeito de subdoses de glyphosate nas trocas gasosas, crescimento e morfologia de P. maximun. O experimento foi realizado em casa-de-vegetação, sendo as plantas cultivadas em vasos, em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos experimentais foram constituídos por uma testemunha (sem aplicação do produto) e nove doses (3,78; 8,10; 16,64; 33,48; 67,70; 135,00; 270,00; 540,00 e 1080,00 g e.a. ha-1). Foram avaliados os parâmetros fisiológicos: fotossíntese líquida, condutância estomática, transpiração, temperatura foliar, concentração interna de CO2. Também foram avaliados o número de perfilhos e intoxicação das plantas e, ao final do experimento determinou-se o acúmulo de massa seca da parte aérea e área foliar. Os dados obtidos foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey a 5% de probabilidade. Quando significativos, realizou-se análise de regressão usando os modelos para as curvas de dose-resposta. Os parâmetros fisiológicos avaliados, foram influenciados positivamente pelas subdoses de glyphosate, apresentando maiores valores que a testemunha. A concentração interna de CO2 foi negativamente afetada, mas houve incremento na temperatura da folha de forma progressiva. Além disso... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Panicum maximum is among most important weed specie in tropical crops, justifying the need to control it, basically with herbicides. Therefore this work aimed to evaluate glyphosate sub dose in the gas exchange, dry mass and morphological in P.maximum. The experiment was conducted in a green house, plants were grown in plots, with a casually randomized design, with four replications. The experimental treatments were constituted with one control ( without application of the product) and nine doses of glyphoste(3.78: 8.1: 16.64: 33.48: 67.7: 135: 270: 540: 1080 g a.e. ha-1 ). It was evaluated: Liquid photosintesys, estomatic conductance, transpiration, leaf temperature, intern CO2 concentration. Besides it was evaluated tillering and intoxication, at the end of the experiment it was determined the aerial dry mass and leaf area. The data obtained was submitted to a variance analysis test and means submitted to a Tukey test at 5 % probability and when significative was used regression using the models for dose response curves. The physiological parameters evaluated where positive influenciated by the glyphosate sub dose showing higher values than the control, furthermore the intern CO2 concentration was negative influenced, beyond it was observed increment in the leaf temperature progressively, also promote an increment for aerial dry mass accumulation and leaf area besides. Further more, concluding that in the Panicum maximun plants submitted to the glyphosate doses of 3,78 to 270 g a.e. ha-1 showed and hormetic effect. / Mestre

Initially the present study was confined to the effects of ultraviolet irradiation on acid-soluble collagen. Such a study was undertaken in order to demonstrate the critical role played by tyrosine and phenylalanine in the intermolecular interaction of the telopeptides protruding from the rigid parent collagen molecule. Since both tyrosine and phenylalanine are photosensitive, and because the collagen telopeptides are relatively rich in these aromatic amino acids, carefully controlled degradation studies involving telopeptide liberation could be made. It became increasingly apparent during the course of investigation, that a better understanding of the subunit composition of thermally denatured acid-soluble collagen was necessary if a satisfactory interpretation of the irradiation studies was to be made. A subsequent study of the subunit composition of thermally denatured acid-soluble collagen resulted in the isolation and characterisation of two major and two minor dimeric components as well as the α- and β - subunits. Three acidic telopeptides and three basic telopeptides were also isolated from acid-soluble collagen during the course of the present study. The presence of the dimeric components while related directly to the method of preparation, suggested that acid-soluble collagen was largely dimeric in nature. Such a conclusion suggested an intermolecular rather than an intraolecular relationship between neutral-salt-soluble and acid-soluble collagen. While it is currently accepted that an intramolecular relationship exists between neutral-salt-soluble and acid-soluble collagen, such a relationship does not satisfactorily explain the very different solubility characteristics displayed by these soluble collagen extracts. With this in mind, and using the study on the subunit composition of thermally denatured acid-soluble collagen as a basis for comparison, the intra and intermolecular relationship between neutral-salt-soluble and acid-soluble collagen was investigated using ultraviolet and gamma irradiation. The effects of ultraviolet and gamma irradiation on soluble collagen preparations proved very similar. Although collagen samples were irradiated in solution from an ultraviolet source; and under anhydrous conditions from a gamma source, much the same degradation mechanism resulted. The initial depolymerisation of dimeric material followed by peptide fission, yielding irradiation-resistant crystalline portions of the parent triple helix, took place in both instances. At the same time, both studies indicated no significant differences in the intra or intermolecular structures of the neutral-salt-soluble and acid-soluble preparations investigated. The dimer content of neutral-salt-soluble collagen preparations was, however, noted to be smaller. To current methods for the preparation of soluble collagens, it may be concluded that such preparations are peptideless to some degree. While the native tropocollagen monomer with its full complement of telopeptide side chains may actively undergo linear polymerisation resulting in fibre formation, the soluble collagen preparations referred to above may only aggregate in a rather random fashion.

Made available in DSpace on 2015-12-10T14:24:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-14. Added 1 bitstream(s) on 2015-12-10T14:30:09Z : No. of bitstreams: 1 000853077.pdf: 575253 bytes, checksum: 168e27dc8ab8049689bf36b6b37d1899 (MD5) / O presente estudo objetivou avaliar os efeitos da suplementação de diferentes níveis de metionina digestível nas dietas de frangos de corte de 1 a 21 dias de idade, sobre o desempenho animal e o rendimento de carcaça, pelo do método tradicional de dose-resposta, e utilizar a técnica de isótopos estáveis através do turnover tecidual para certificar este procedimento de exigência nutricional. Foram realizados dois ensaios em delineamento inteiramente casualizado, com sete tratamentos que consistiram de níveis de metionina digestível para as fases pré-inicial e inicial, respectivamente: 70% (0,320 e 0,307), 80% (0,360 e 0,331), 90% (0,410 e 0,380), 100% (0,450 e 0,417), 110% (0,500 e 0,460), 120% (0,540 e 0,510) e 130% (0,591 e 0,540) de metionina digestível correspondentes às exigências preconizadas por Rostagno et al. (2011). No ensaio I foram utilizados 875 pintos de corte de um dia de idade alojados em 35 unidades experimentais e avaliou-se o desempenho e o rendimento de carcaça. No ensaio II foram alojados 567 pintos de corte de um dia de idade e avaliou-se o turnover do 13C no músculo peitoral e fígado. Todos os animais foram submetidos à dieta a base de arroz e farelo de soja do primeiro aos 21 dias de idade. No ensaio I foi verificado melhora no desempenho de 1 a 7 dias de idade nos tratamentos 100% e 120% para peso corporal e ganho de peso e de 1 a 21 dias de idade nos tratamentos 100%, 110%, 120% para ganho de peso e peso corporal. Observou-se melhora na conversão alimentar com os tratamentos 100%, 110%, 120% e 130%. Os tratamentos 100% e 120% apresentaram melhora no rendimento de peito, o 110% para gordura abdominal e o 120% para o peso do fígado aos 21 dias de idade. No ensaio II foi verificado diminuição da meia-vida e aumento da taxa metabólica para o músculo peitoral no tratamento 130% e para o fígado no tratamento 80%. Pode-se observar que os tratamentos 100%, 11 ... / The present study aimed to evaluate the effects of different levels of digestible methionine in broiler diets on performance, carcass yield through the traditional method of dose-response, and use the stable isotopic of tissue turnover to certificate this procedure of nutritional requirement. Two trials were conducted in a completely randomized design with seven treatments that consisted in levels of digestible methionine to pre-starter and initial phase, respectively: 70% (0,320 e 0,307), 80% (0,360 e 0,331), 90% (0,410 e 0,380), 100% (0,450 e 0,417), 110% (0,500 e 0,460), 120% (0,540 e 0,510) e 130% (0,591 e 0,540) of digestible methionine corresponding to the requirements recommended by Rostagno et al. (2011). In the first trial, 875 one day old chicks were housed in 35 pens to evaluate the performance and carcass yield. In the second trial, 567 one day old chicks were housed to determinate the turnover of carbon-13 in the pectoral muscle and liver. All birds were fed a diet based on rice and soybean meal (predominantly C3) for the first 21 days of life. In the first trial was verified improved performance at 7 days old on treatments 100% and 120% for body weight and weight gain and at 21 days old on treatments 100%, 110% and 120% for body weight and weight gain. It was noted improving on feed conversion with treatments 100%, 110%, 120% and 130%. The treatments 100% and 120% showed improvement on breast yield, the 110% to fat abdominal and the 120% for liver weight at 21 days old. In the second trial was verified reduction of half-life and increase of metabolic rate to the breast muscle on treatment 130% and for liver on treatment 80%. It could be noted that treatments 100%, 110% and 120% improvement the animal performance

Thesis (MTech Biomedical Technology)--Cape Peninsula University of Cape Town, 2005 / In clinical radiotherapy, experiments are performed to determine optimal conditions of the radiation prior to radiotherapy. These experiments focus on the relative biological effectivness(RBE) determination and are predominantly applied in high linear energy transfer (LET) radiations i.e. fast neutrons, as the RBE values for such radiations vary greatly. In general, the RBE of a certain radiation relative to a given reference radiation flCo gamma) varies widely with the energy, dose, dose rate, fractionation, type of tissue and end-point used. Experience with neutron therapy at iThemba LABS has shown that treatment with more fractions and lower doses per fraction may be beneficial for some patients. To calculate the iso-effective treatment dose needed, an appropriate alp ratio for early effects is needed. In this study, the repair of mouse jejunum was measured for split-dose irradiations to determine if a suitable alP ratio for neutrons could be estimated using the known value for gamma rays and the applicable RBE.. Crypt stem cell survival was measured 3.5 days after split-dose exposures to p(66)/Be neutrons and 6OCo gamma rays. Dose response curves for both treatment modalities and for both acute and fractionated exposures were constructed by counting crypts of Leiberkhiin at the base of the villi in haematoxylin and Eosin-stained sections of mouse jejunum. Using a RBE value of 1.64 and an alP ratio of 7Gy noted for tbe fractionated photon exposures, an alP ratio of 11.5 IV could be estimated for neutrons.

Thesis (DTech (Biomedical Technology))--Cape Technikon, 2001 / Ionising radiation has the ability to induce, inter alia, DNA damage and is well established as a causative agent of carcinogenesis and mutagenesis. The effects of high doses of short duration have been well documented, whereas the effects of continuous exposure to low doses of ionising radiation have not, nor are they as clearly understood and current risk estimates are largely extrapolated from high-dose data of atomic bomb survivors. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two areas in the mine, with external radiation levels measuring around 20 µSv/h (low dose) and 100 µSv/h (high dose). A control group of bats was collected from a cave with no detectable radiation above normal background levels. The most frequently encountered genetic event in human malignancy is the alteration of the p53 gene. Mutant p53 proteins have a longer half-life than the wild-type variant and accumulate to high levels in the nucleus of tumour cells. The study showed that not only was there a significant increase in p53 positive cells of radiation exposed bats, but also in the degree of positivity, especially in the cells lining the bronchioles of the lungs. Although experimental studies have shown that exposure to radiation may lead to the onset of fibrosis and an inflammatory response in the lung and other tissues, the magnitude of the dose exposure was not comparable to this study and histological examination of bat lung and liver tissues showed no morphological changes in radiation exposed bats when compared to the control group. It has been documented that chronic radiation exposures may give rise to a number of specific haematological defects which are collectively termed "preleukemia" or myelodysplastic syndrome. Full blood counts on bat samples showed a significant decrease in the MCV indicating microcytic erythrocytes from the radiation exposed bats. Differential counts performed on the peripheral blood of the bats showed a marked neutropenia. Neutrophils also showed marked dysplasia including psuedo-Pelger Huet cells in radiation-exposed bats. Cytochemical analysis using DAB myeIoperoxidase showed that control bats had hypogranular neutrophils andradiation-exposedbats had largely '1granularneutrophils. Bonemarrow biopsies were taken from both control and radiation-exposed bats and evaluated for ceIlularity, granulocyte: lymphocyte: erythrocyte (GLE) ratio and megakaryocyte morphology. A hypocelIular bone marrow, a decreased granulocytic haematopoeisis and dysplastic megakaryocyte morphology were observed in radiation-exposed bats. Mineralisation of bone osteoid was determined using image analysis and showed a highly significant decrease in the bone matrix from radiation-exposed bats. All haematological features observed are congruent with current literature describing secondary (radiation-induced) myelodysplastic syndrome.

In the investigation of radiation accidents, it is of great importance to estimate the dose absorbed by exposed persons in order to plan their therapy. Although occasionally in these situations physical dose measurements are possible, most often biological methods are required for dose estimation. The aim of this investigation was to assess the suitability of the cytokinesis blocked (CB) micronucleus assay as a biodosimetric method using lymphocytes irradiated in vivo. The approach adopted to achieve this was to estimate whole body doses by relating micronuclei yields in patients undergoing radiotherapy treatment with an in vitro radiation dose-response curve. These biologically derived estimates were then compared with the corresponding doses obtained by physical measurement and calculation. As a first approach a study was performed of the in vitro dose-response of gamma-ray induced micronuclei following cytokinesis-block in the lymphocytes of peripheral blood samples obtained from 4 healthy donors. The results indicated that the distribution of the induced micronuclei were overdispersed. Furthermore, a linear dose-response relationship was established when a curve was fitted to the data by an iteratively reweighted least squares method. By means of an analysis of covariance it was demonstrated that this result is in agreement with the dose-response relationships found by various other workers (Fenech et al., 1985; Fenech et al., 1986; Fenech et al., 1989; Balasem et al., 1992, and Slabbert, 1993). To assess the suitability and accuracy of dose assessment using the CB micronucleus assay for in vivo exposure of lymphocytes, blood samples obtained from 8 patients undergoing radiotherapy before, during and after treatment were examined. The physical doses of these patients were determined according to conventional radiation treatment plans and cumulative dose-volume histograms. The dose-volume histograms permitted calculation of integral doses and subsequently the estimate of equivalent whole-body doses. The results of the CB micronucleus assay applied to peripheral blood lymphocytes of 6 patients undergoing fractionated partial-body irradiation showed a dose-related increase in micronucleus frequency in each of the patients studied. This demonstrated that micronuclei analysis may serve as a quantitative biological measure of such exposures. The pooled data of these patients compared to the pooled data of the healthy donors show that there was no statistically significant difference between in vitro and in vivo results, however a slightly lower induced micronuclei frequency was observed after in vivo exposure. When the biological dose estimates for equivalent whole-body doses obtained from the in vitro dose response curve were compared with calculated physical doses, it was found that: biologically estimated dose = 0.936 physical dose. However, there was inadequate statistical evidence to discard the hypothesis that the gradient of the equation was equal to one. Therefore, the analysis of micronuclei induced in lymphocytes in vivo yields highly quantitative information on the equivalent whole-body dose. The negative binomial method was used for analysing the micronucleus data from two patients who received single, relatively larger tumour doses of 10 Gy each, with the objective to obtain estimates of the exposed body fraction and the dose to this fraction. The dose estimates to the irradiated volume were found to be within 30% of the physical tumour dose. The irradiated volume estimates seemed to be higher than the physically calculated volumes but by discarding the correction for the loss of cells due to interphase death the agreement was good between the physically and biologically determined integral doses. This study has revealed that the CB micronucleus assay appears to offer a reliable, consistent and relatively rapid biological method of whole body dose estimation. It is recognised that further corroborative work using the techniques described in this thesis is required for estimating localized exposure.

Many studies addressing the toxicity of silver nanomaterials have found that smaller sized silver nanoparticles are usually more toxic to organisms and in cell culture than particles of larger sizes yet it is not entirely clear why. We investigated the size dependent toxicity of silver nanoparticles by measuring the response of embryonic zebrafish (Danio rerio) following exposure to a library of thirteen distinct silver nanoparticle size distributions with mean diameters between 8.9 nm and 112.6 nm. Data analysis using dose���response modeling revealed that silver nanoparticles (AgNP) induced embryo toxicity that is dependent on the total surface area and not on the mass or particle number in solution. Included in this study is a comparison between embryo toxicity induced by silver nitrate (AgNO���) and AgNPs for cardiovascular endpoints, as well as an investigation into the influence of the chorion on AgNP toxicity. This study demonstrates the importance of using alternative dose metrics in nanotoxicology, and highlights the value of using the embryonic zebrafish to explore nanomaterial structure activity relationships. / Graduation date: 2013

Most breast cancer patients undergo radiation diagnostics and are also treated with radiotherapy. In addition to being an important treatment modality, ionizing radiation (IR) is a potent tumour-causing agent that has been linked to breast cancer development. However, the exact molecular etiology of IR-induced mammary gland carcinogenesis remains unknown. We set out to analyze the role of DNA methylation in mammary gland responses to low dose IR using a well-established rat model. We also studied low dose IR effects on global gene expression and microRNAome. We found that exposure to low, mammography-like dose of IR led to a significant loss of global DNA methylation in rat mammary gland tissue. Furthermore, low dose IR significantly affected rat mammary gland transcriptome and microRNAome. The datasets generated within the scope of this thesis may be used to identify novel predictive biomarkers for assessment of the magnitude of IR effects on mammary gland tissue. / xi, 120 leaves ; 29 cm

Thesis--University of Oklahoma. / Bibliography: leaves 71-78.