Made available in DSpace on 2014-06-11T19:28:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-11-25Bitstream added on 2014-06-13T18:57:09Z : No. of bitstreams: 1 000736296.pdf: 4233456 bytes, checksum: d4f70261c2f3ef33e27f9d851acefc69 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Doenças neurodegenerativas são definidas como distúrbios que acarretam na perda progressiva de estrutura e/ou função, e até mesmo morte de células neuronais especificas, em diferentes distribuições anatômicas, e, consequentemente, dando origem a diferentes sintomas clínicos. Entre as varias doenças neurodegenerativas a doença de Alzheimer (DA) é a principal e a mais comum forma de demência. A DA é uma condição progressiva complexa que envolve interações sequenciais de cascatas patológicas, incluindo a interação dos peptídeos β-amiloides (βA) que se agregam levando ao desenvolvimento de placas senis, e a hiperfosforilação e agregação da proteína tau formando emaranhados neurofibrilares (ENF), juntamente a processos associados, como a inflamação e o estresse oxidativo. O fator de necrose tumoral alfa (TNF-α) é uma das principais citocinas pró-inflamatórias cujos níveis elevados são observados em diversas doenças neurodegenerativas. O óxido nítrico (NO) é uma importante molécula de sinalização na modulação da plasticidade sináptica e está associada ao processo de aprendizagem e memória, assim como seus efeitos neuroprotetores quando presente em baixas concentrações. Assim, compostos derivados ftalimídicos, capazes de inibir TNF-α, poderiam reduzir o processo de neuroinflamação que é descrita na DA, retardando a progressão da doença, e derivados doadores de NO poderiam contribuir na plasticidade sináptica, cognição e memória dos pacientes acometidos pela DA. Foi objetivo deste trabalho a obtenção dos compostos Lapdesf FUR-FD I-VI, planejados por meio da estratégia de hibridação molecular entre a subunidade ftalimídica e o núcleo furoxânico. Os compostos obtidos foram avaliados para determinar o potencial efeito anti-inflamatório através do modelo de inflamação aguda (edema de pata), a determinação do Log P experimentalmente para avaliar sua capacidade de permear a barreira... / Neurodegenerative diseases are defined as disorders that result in progressive loss of structure and/or function, and even cell death in neuronal specific in different anatomical distributions, and hence giving rise to varying clinical symptoms. Among the various neurodegenerative diseases Alzheimer's disease (AD) is the main and most common form of dementia. AD is a progressive condition that involves complex interactions and sequential pathological cascades, including the interaction of β-amyloid peptide (βA) which clump together leading to the development of senile plaques, and hyperphosphorylation and aggregation of tau forming neurofibrillary tangles (ENF) along the associated processes, such as inflammation and oxidative stress. The tumor necrosis factor alpha (TNF-α) is a major proinflammatory cytokines whose high levels are observed in several neurodegenerative diseases. Nitric oxide (NO) is an important signaling molecule in the modulation of synaptic plasticity and its correlation with the process of learning and memory, as well as its neuroprotective effects when present in low concentrations. Thus phthalimidic derived compounds capable of inhibiting TNF-α , could reduce the neuroinflammation process that is described in AD, slowing the disease progression, and NO donors derived may contribute to synaptic plasticity, cognition and memory of patients affected by AD. This work aims to obtain the compounds (Lapdesf FUR-FD I-VI), designed by molecular hybridization strategy between the subunit and core phthalimidic and furoxan. The compounds obtained were evaluated for potential anti-inflammatory effect through the model of acute inflammation (paw edema), their ability to permeate the blood-brain barrier (BBB) using a tool of the partition coefficient (log P) obtained experimentally mutagenicity with the in vivo micronucleus test in reticulocytes obtained in peripheral blood, the ability of the compounds to inhibit the ...

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Weed infestation is one of the yield limiting factors in crop production. Weeds have negative effect on crop growth and productivity due to competition, allelopathy or hosting other harmful organisms. For large-scale wheat production, the use of wide spectrum pre-emergence or post-emergence herbicides remains the most valuable weed control tool. In South Africa, annual grass weeds are a major wheat production constraint, which is usually managed through application of pre-emergence herbicides. Due to limited water availability and low soil moisture content, these herbicides can often become ineffective and result into high weed infestations, which then have to be managed by manual cultivation or post-emergence herbicidal applications. However, there are no effective selective post-emergence herbicides available to control grass weeds in wheat. There is also limited option to use broad-spectrum post-emergent herbicides because they non-selectively kill the crop and weeds. Consequently, the use of herbicide resistant crops is a viable weed management system in wheat production. Breeding herbicide resistant crop varieties would allow farmers to safely use post-emergence herbicides without damaging the crop. Subsequently yield and quality losses will be reduced significantly. Thus, the development of herbicide resistant crop varieties through mutation breeding is a novel approach for effective weed management under both small-scale and commercial farmers. Mutagenesis has been recognized as one of the most efficient method to induce genetic variation in plants. Through induced mutations, development of new variants is possible that could be manipulated in plant breeding programs. Mutation leads to alteration of various traits in crop plants including plant height, improved nutritional quality, shorter growing period, increased tolerance or resistance to abiotic and biotic stresses. Ethylmethanesulphonate (EMS) is one of the most widely used chemical mutagens to induce mutagenesis in crop plants. The objectives of this study were to: 1) determine the optimum EMS concentration, treatment temperature and duration that would provide desired germination percentage and vigorous and healthy seedlings for effective mutagenesis in wheat, 2) investigate variations in agro-morphological traits in two selected wheat varieties (SST56 and SST875) after EMS mutagenesis and 3) select herbicide resistant wheat germplasm after inducing genetic variation using EMS using two selected wheat varieties (SST56 and SST875). The objectives were achieved through three independent studies as outlined below: In the first study seeds of four selected wheat varieties (B936, B966, SST387 and SST875) were treated in two replicates with three EMS concentrations (0.3, 0.5, and 0.7%), three temperature regimes (30, 32.5 and 35 °C) at four time durations (0.5, 1, 1.5 and 2 hrs). Results showed highly significant interactions (P<0.01) among varieties, EMS concentrations, temperature and exposure time on seedling emergence, germination and seedling height. Seeds treated with the highest EMS dose (0.7%), temperature (35ºC) and long exposure time (2 hr) showed delayed emergence by 18 days. At 30ºC, 0.5hr and 0.3% EMS varieties B936, B966 and SST875 had early emergence (6 days). B936 and SST387 had 50% while B966 and SST875 had 53% and 57% germination, respectively. These results were observed at EMS level of 0.7%, 300C and 1.5 hr exposure time in B936 and EMS at 0.5%, 350C and 1.5 hr in B966. SST387 and SST875 required EMS dose at 0.5%, 32.50C and 2 hr treatment time. Other low or high treatment combinations were invariably ineffective comparedto untreated control. During the second study two selected varieties (SST56 and SST875) were subjected to EMS mutagenesis using 0.5% v/v EMS at 32.5oC for 1 hr. Field trials were carried out at Ukulinga research farm of the University of KwaZulu-Natal in the randomized complete block design with two replicates. Data on nine important agro-morphological traits were collected and analyzed using the analysis of variance (ANOVA), correlation and principal component analysis (PCA) procedures. Significant variations were found among the agro-morphological traits between M1 individuals compared to untreated checks. The mutagenesis significantly reduced seed germination in the field at 40% in both varieties. The treatment significantly delayed days to heading by 8 days and shortened days to maturity by 13 days in both varieties. EMS treatment also significantly reduced plant height at 18 cm in SST56 and 21 cm in SST875 and spike length reduced by ~2.5 cm in both varieties. Plant height had positive and significant correlation with number of tillers, number of seeds per spike, flag leaf length and 100 seed weight. However, it had negative correlation with the number of days to maturity. The PCA revealed that three principal components (PC1, PC2 and PC3) accounted to 57% of the total variations among the agro-morphological traits in both varieties. PC1 alone contributed to 27.7% of the variation which was well-correlated with plant height (0.767), tiller number (0.812), number of seeds per spike (0.599) and seed yield (0.720). PC2 explained 15.6% of the variation and well-correlated with germination percentage (0.784), spike length (0.554) and flag leaf length (0.772). PC3 accounted to 12.4% of the variation and had negative correlation with days to maturity (-0.730). In the last study, seeds of two selected wheat varieties (SST56 and SST875) were treated with EMS at 0.5% concentration for 2 hr at 32.5ºC. Treated seeds and comparative controls were planted at the experimental farm of the University of KwaZulu-Natal using the randomized complete block design. Four weeks after planting M1 plants and untreated standard checks were sprayed with two herbicides, i.e. metsulfuron-methyl and bromoxynil at three different doses viz. 2x, 4x and 8x above the recommended rate of 4 g ha-1 and 2 kg ha-1, respectively. Two weeks after the treatment herbicide resistance were assessed. Results showed significant difference among varieties, tested herbicides and doses used. The EMS treated wheat lines showed variable degree of herbicide resistance compared to untreated controls. Overall, the study established the requirement of variety specific EMS dose and treatment temperature and duration that could be used for inducing large-scale mutation to select targeted mutant individuals in wheat. Further, the study found that EMS has the potential to increase agro-morphological variations in wheat to select useful and novel mutants with desired phenotypic traits and herbicide resistance which will be subjected for further selections to identify stable and herbicide resistance lines. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Il ricino (Ricinus communis L.) è una tra le dieci principali colture oleaginose a livello mondiale. La ricina, eliminata nei processi industriali per la produzione di olio di ricino, costituisce un rischio sia per lo sfruttamento della pianta come biomassa per la generazione di biocarburanti vegetali di seconda generazione, sia per la possibilità di ottenere scorie tossiche dalla lavorazione del materiale. L’utilizzo di tecniche di mutagenesi chimica, associata ad AFLP e metodiche di sequenziamento bersaglio specifiche (TILLING) hanno dimostrato la possibilità di ottenere e riconoscere, in tempi relativamente brevi e in modo specifico, mutazioni nel genoma d’interesse. A partire da una popolazione monovarietale di ricino, sono stati messi a punto diversi trattamenti (basati su EMS ed MNU), al fine di ottenere una popolazione mutagenizzata chimicamente al cui interno ricercare piante prive, o con un contenuto ridotto, di ricina nel seme e di conseguenza caratterizzate da un maggior valore agronomico ed economico. In seguito all’autoimpollinazione delle piante sopravvissute, analisi AFLP e di sequenziamento sulle generazioni successive hanno mostrato come le piante tendano ad accumulare variazioni nel loro genoma rispetto alla generazione precedente. Dall’analisi di sequenza di circa 1 Mb del gene per la ricina nella popolazione mutagenizzata non è emerso nessun cambiamento nella sequenza nucleotidica, in accordo con i risultati di altri studi in cui si è visto come la frequenza di mutagenesi possa variare con la specie considerata. / Castor (Ricinus communis L.) is one of the ten major oil crops worldwide. Ricin, eliminated in industrial processes for the production of castor oil, constitutes a risk to both the exploitation of the plant as a biomass to generate second-generation biofuels, both for getting toxic waste from the processing of the material. The use of chemical mutagenesis techniques, AFLP and methods associated with specific target sequences (TILLING) have demonstrated the ability to obtain and recognize, in a relatively short time, and specifically, mutations in the genome of interest. Starting from a population of castor-variety, have been developed different treatments (based on EMS and MNU), in order to obtain a chemically mutagenized population of plants with a reduced content of ricin in the seed and therefore characterized by a greater agronomic and economic value. After self-pollination of the survived plants, AFLP analysis and sequencing showed how plants tend to accumulate changes in their genome than the previous generation. A sequence analysis of about 1 Mb of the gene for ricin in mutagenized populations has revealed no change in the nucleotide sequence, in agreement with results of other studies in which we have seen that the frequency of mutation may vary with the species under consideration.

Aspartokinase is the first enzyme of the aspartate family amino acids biosynthetic pathway. Cephamycin C is a &amp / #946 / -lactam antibiotic produced as a secondary metabolite via the enzymatic reactions in the lysine branch of this pathway in Streptomyces clavuligerus. The aspartokinase activity of S. clavuligerus is under concerted feedback inhibition by two of the end product amino acids, lysine plus threonine. It is also known that carbon flow through the lysine branch of the aspartate pathway is rate limiting step in the formation of cephamycin C. Therefore, genetic alterations in the regulatory regions of the aspartokinase enzyme are expected to lead to an increased cephamycin C production. The aim of this study was to obtain S. clavuligerus mutants that possess aspartokinase enzyme insensitive to feedback inhibition by lysine and threonine, identification of the mutation(s) accounting for the resistance being the ultimate goal. For this aim, chemical mutagenesis was employed to increase random mutation rate and a population of lysine anti-metabolite resistant S. clavuligerus mutants that can grow in the presence of S-(2-aminoethyl)-L-cysteine was obtained. The mutants were screened for their aspartokinase insensitivity via enzyme assays and one mutant exhibiting the highest level of deregulation was assessed for its cephamycin C production. The results revealed a 2-fold increase in specific production of the antibiotic. As a member of &amp / #946 / -lactam class antibiotics, cephamycin C has an importance in medicine. Therefore, the mutant strain obtained might be a candidate for industrial production of the compound.

MSCAGR ( Plant Production) / Department of Plant Production / See the attached abstract below

Sorghum (Sorghum bicolor) is an important cereal crop in sub-Saharan Africa. The parasitic weed Striga hermonthica is a major biotic constraint to sorghum production. A novel technology where planting seeds are coated with herbicide to kill Striga that attach to the roots of the host has been shown to be effective in protecting the cereal crop from Striga damage. However, the host plant must have herbicide tolerance. This technology has not been tested in sorghum because there are no herbicide tolerant sorghum varieties available in Kenya and is, therefore, unavailable for subsistence farmers. One of the ways in which genetic variation can be enhanced and herbicide resistance developed is through chemical mutagenesis with ethyl methane sulfonate (EMS). The objectives of this project, therefore, were to: 1) identify sorghum production constraints through farmer PRA in order to determine breeding priorities.in two Striga endemic districts in western Kenya; 2) develop an EMS mutagenesis protocol for sorghum and to enhance the genetic variability of the crop using chemical mutagenesis; 3) evaluate EMS-derived sorghum mutants for improved agronomic performance; 4) develop acetolactate synthase (ALS) herbicide resistance in sorghum and to characterize the mode of inheritance of the trait; 5) determine the effect of herbicide coating of seed of herbicide tolerant sorghum on Striga infestation. In order to determine breeding priorities and constraints in sorghum production and the likelihood of adoption of herbicide seed coating technology, a survey involving 213 farmers was conducted in two Striga endemic rural districts of Nyanza province in Kenya. Results indicated that local landraces like Ochuti, and Nyakabala were grown by more farmers (> 60%) than the improved varieties like Seredo and Serena (48%). Popularity of the landraces was linked to Striga tolerance, resistance to drought, bird damage and storage pests, yield stability and high satiety value. Major constraints to sorghum production were drought, Striga weed, storage pests, bird damage and poverty among the rural farmers. Important characteristics farmers wanted in new varieties were Striga and drought resistance, earliness, resistance to bird and weevil damage and good taste. Striga infestations in sorghum fields were > 70%. Cultural Striga control options were considered inadequate while inorganic fertilization and chemical control were considered effective but unaffordable. Farmers’ willingness to pay a premium of over 30% for a Striga solution gave indication that herbicide seed coating if effective could be adopted by farmers. As a prerequisite to development of herbicide resistance, a comparative study was carried out to determine optimum conditions for mutagenesis and to induce genetic variation in the sorghum. Two sorghum varieties were mutagenized using varying concentrations (0.1 to 1.5% v/v) of EMS and two exposure times (6h and 12h). In laboratory and greenhouse experiments, severe reduction of sorghum root and shoot lengths indicated effective mutagenesis. The LD50 based on shoot length reduction was 0.35% and 0.4% EMS for 6h for Seredo and Kari/mtama-1, respectively. The highest mutation frequency based on chlorophyll abnormalities was 56% for 0.3% EMS for 6h. In the M2 generation, phenotypic variances for panicle characteristics were increased on treatment with EMS. However, significant effects of exposure time and variety indicated the necessity of genotype optimization for some traits. In order to determine the significance of mutation breeding in sorghum, 78 mutant lines derived from EMS mutagenesis, their wild type progenitor (Seredo) and two local checks (Kari/mtama-1 and Serena) were evaluated for agronomic performance in two locations in Kenya. There were significant (P = 0.05) effects among entries for grain yield, 1000-seed weight and visual scores for height uniformity, head exertion, head architecture and overall desirability. The highest yielding entry-mutant line “SB2M13” had a yield of 160% and 152% relative to the wild type (Seredo) and the best check Kari/mtama-1, respectively. Mutant line “tag27” had the highest 1000-seed weight which was 133% relative to the wild type. Seven mutant lines were rated superior to the wild type for panicle characteristics, head exertion and overall desirability. However, the majority of mutants were inferior to the wild type for most characteristics. Superior mutant lines may be developed into direct mutant varieties after multi-location trials or used as breeding material for sorghum improvement. In order to develop acetolactate synthase (ALS) herbicide resistance in sorghum, over 50,000 seeds of Seredo were mutagenized with 0.3% EMS. Over four million M2 plants were screened using 20g ha-1 of the ALS herbicide, sulfosulfuron. Five mutants (hb46 hb12, hb462, hb56 and hb8) survived the herbicide treatment and were confirmed to be tolerant. Mutant lines displayed differential herbicide tolerance, and the general order of tolerance after spray or seed coat application was hb46 > hb12 > hb462 ~ hb56 > hb8. The LD50 values for herbicide application as a spray, or seed coat, showed mutant lines to be up to 20 and 170 fold, respectively, more resistant than the wild type. Chi square analysis of data from herbicide screening of F2 generation of mutant X wild type crosses indicated no difference from the Mendelian segregation of 1:2:1 indicating the herbicide tolerance was inherited as a single semi-dominant gene. Mutant X mutant crosses did not show allelism indicating that the tolerance in all five mutants could be a result of the same gene mutation. To determine effect of herbicide seed coating on Striga infestation, the five herbicide tolerant mutant lines, hb46, hb12, hb462, hb56 and hb8 and the wild type progenitor Seredo were coated with varying concentrations (0.5-1.5% g ha-1) of sulfosulfuron and planted in a Striga endemic field. There were significant (P=0.05) effects of herbicide concentration on Striga density, Striga flowering and seed set, and sorghum plant stand and biomass. All treatments with herbicide coated on sorghum seeds had lower Striga emergence. Coating sorghum seed with 1g ha-1 sulfosulfuron reduced Striga infestation, Striga flowering and Striga seed set by 47%, 52% and 77%, respectively, and was considered the most effective rate as it did not result in sorghum biomass reduction. Mutants displayed differential herbicide tolerance and Striga resistance. Combining seed coating with high herbicide tolerance and inherent Striga resistance would be most effective for Striga control. Overall, the study showed that EMS mutagenesis is effective in inducing variation in sorghum for several traits including herbicide resistance. The mutants developed in this study will be important for sorghum breeding and for protection of sorghum against the Striga weed. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2009.

The role of meat consumption in the development of cancer, including colorectal cancer (CRC), has been subject of much investigation in recent years. The observation of geographical variation in CRC incidence and increased CRC risks in populations consuming high levels of meat prompted researchers to hypothesise a link between meat and CRC. An area of particular interest in CRC pathogenesis is the meat-derived compounds such are heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), and meatderived mutagenic activity. Australia is among the countries with high incidence of CRC and also high levels of per capita meat consumption. Hence, clarifying the possible link between meat consumption and the risk of CRC in order that this can be translated into preventive dietary recommendations for the public is important. The objective of this thesis was to examine whether meat consumption is related to risk of CRC in an Australian population. The term meat consumption in this thesis means meaures of consumption of red and white meat that incorporate frequency and cooking method. The following hypotheses were investigated: 1. Increasing intake of meat prepared by methods that involve higher cooking temperature and time is positively associated with the risk of CRC; 2. Increasing exposure to meat-derived heterocyclic amines (HCAs) is positively associated with the risk of CRC; 3. Higher levels of exposure to polycyclic aromatic hydrocarbons (PAHs) from meat consumption is a risk factor for CRC; 4. Exposure to meat-derived mutagens increases the risk of CRC.