Combretum species are used in many cultures in folk medicine for treatment of microbial infections and several inflammatory conditions (abdominal pains, headache and toothache). There are two possible mechanisms to explain the use of plants extracts to treat microbial infections. A direct effect involves the action of active agents in the extracts on the microorganism tested and the indirect effect involves the stimulation of the host immune system to overcome the effects of microorganisms via the host immune system. Traditional healers use mainly aqueous extracts and in all Combretaceae we have studied, these extracts had hardly any in vitro antibacterial activity. A search of the literature confirmed our observations, aqueous plants extracts of many plant species usually have very little direct in vitro antimicrobial activity. One would expect that aqueous extracts would have higher anti-oxidant activities and may stimulate the immune system of patients thereby combating the infection indirectly. This possibility prompted the investigation of the antioxidant potential of more polar extracts of Combretum species. Methanol extracts of leaves of ten different Combretum species were evaluated for qualitative antioxidant activity by spraying TLC chromatograms of leaf extracts with 2, 2-diphenyl-1-picrylhydrazyl (DPPH). Compounds with anti-oxidant activity bleached the purple colour. Leaf extracts of Combretum apiculatum subspp apiculatumhad the most antioxidant compounds. This species was consequently selected for further examination. Anti-oxidant directed fractionation of the leaf extracts of C. apiculatum led to the isolation of four antioxidant compounds from ethyl acetate and butanol soluble fractions. The structures of the compounds were determined by spectral analyses (1H-NMR, 13C-NMR and MS) and identified as cardamomin (1), pinocembrin (2), quercetrin (3) and kaempferol (4). These compounds occur commonly in plant extracts, but the anti-oxidant activities of all these compounds were not known previously. In a quantitative antioxidant assay using DPPH with L-ascorbic acid as positive control, the more polar fractions (ethyl acetate and butanol) obtained by solvent-solvent fractionation had the highest activity among the extracts with EC50 values of 3.91 ± 0.02 and 2.44 ± 0.02 µg/mL respectively. Of the isolated compounds, quercetrin (3) and kaempferol (4) had strong antioxidant activity with EC50 values of 11.81 ± 85 and 47.36 ± 0.03 µM respectively. Cardamomin (1) and pinocembrin (2) did not have strong activity as these compounds could not scavenge 50% of the DPPH radical at the highest concentration (200 µM) tested. L-ascorbic acid was used standard antioxidant agent (EC50 = 13.37 ± 0.20 µM or 2.35 µg/mL). The antioxidant activity of the isolated compounds supported structure-activity relationships developed by other authors. The cytotoxicity of cardimonin and pinocembrim was evaluated using MTT assay with, berberine as positive control and DMSO as negative control. At higher concentrations than 50 µg/ml of cardimomin or pinocembrin the cells were not viable. Cardimomin was more toxic to the cells (LC50 of 1.97 µg/ml) than pinocembrin (LC50 of 29.47 µg/ml) and even the positive control, berberine (LC50 of 12.35 µg/ml). The presence of these antioxidants could provide a rationale for the ethnomedicinal use of this species for the treatment of inflammatory conditions in traditional medicine. It appears that the antimicrobial activity of aqueous plant extracts may be related to the antioxidant activity leading to a stimulated immune system rather than antimicrobial activity per se Because the crude polar extract had an antioxidant activity half that of L ascorbic acid, the rationale for using these plants by traditional healers becomes clear. The toxicity of cardomomin is a warning that the safety of these extracts should be evaluated in in vivo assays. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2007. / Paraclinical Sciences / unrestricted

No description available.

The subject of soil absorption is an old one, dating back to before 1850. The nature of soil absorption has been, and still is, a puzzle, in spite of the vast amount of work that has been done in the last few years. Two theories have been held as the cause of the absorption. The first is that the absorption is chemical, the compounds being changed into insoluble ones by double decomposition. The second is that the salts or radicals are physically held, that is, adsorbed by the soil particles. These theories have been held separately and combined.

Resurrection plants are a polyphyletic group of angiosperms which display true desiccation tolerance - the ability to survive near complete loss of cellular water for extended periods, while recovering metabolic competence upon watering. This is achieved by employing tailored protection behaviours depending on the relative state of (de)hydration. Recent work has raised interest in desiccation associated changes related to tissue destiny in desiccation tolerant vegetative tissues. In this thesis, physiological and transcriptomic techniques were used to characterize such a phenomenon in the homoiochlorophyllous dicot resurrection plant Craterostigma pumilum. Detailed phenotypic observation and pulse-amplitude-modulation fluorometry were used to identify the critical water contents at which key physiological changes occur in leaves of C. pumilum and how this relates to desiccation-associated differentiation between leaf Tip and Base tissues. This was followed by transcriptomic analyses and comparison between these two tissues, to identify potentially key processes involved in desiccation associated tissue differentiation. All findings were then synthesised with existing information reported on for other resurrection plant species to create a theoretical model of desiccation-associated tissue differentiation. This differentiation phenomenon is shown to be transcriptionally initiated during the desiccation commitment stage of the C. pumilum dehydration cycle but is only realised phenotypically during early rehydration and after initial water movement through the leaf tissues. This work provides strong evidence for the existence of desiccation-associated tissue differentiation in C. pumilum and highlights the potential involvement of the phytohormone auxin in the determination of leaf tissue responses to progressive dehydration and anhydrobiosis in resurrection plants.

This investigation deals with the suspension of a lightweight medium-class vehicle for four passengers with a curb weight of 1000 kg. The suspension layout consists of a transversal leaf spring and is supported by an active air spring which is included in the damper. The lower control arms are replaced by the leaf spring ends. Active ride height control is introduced to compensate for different vehicle load states. Active steering is applied using electric linear actuators with steer-by wire design. Besides intense use of light material the inquiry should investigate whether elimination of suspension parts or a lighter component is concordant with the stability demands of the vehicle. The investigation is based on simulations obtained with MSC Software ADAMS/Car and Matlab. The suspension is modeled in Adams/Car and has to proof it's compliance in normal driving conditions and under extreme forces. Evaluation criteria are suspension kinematics and compliance such as camber, caster and toe change during wheel travel in different load states. Also the leaf spring deflection, anti-dive and anti-squat measures and brake force distribution are investigated. Based on a simplified version of the leaf spring suspension design a full vehicle model is created. The comparison between the suspension models evaluates the same basic suspension parameters to ensure the compliance. Additionally roll rate and understeer gradient are investigated. It can be shown that the vehicle equipped with transversal leaf spring instead of lower control arms fulfils the set kinematics and compliance requirements. Road holding performance is assured for normal driving conditions on public roads.

Much is known about how organs acquire their identity, yet we are only beginning to learn how their shape is regulated. Recent work has elucidated the role of coordinated cell division & expansion in determining plant organ shape. For instance, in Antirrhinum, leaf shape is affected in the cincinnata (cin) mutant because of an alteration in the cell division pattern. CIN codes for a TCP transcription factor and controls cell proliferation. It is unclear how exactly CIN-like genes regulate leaf morphogenesis. We have taken biochemical and genetic approach to understand the TCP function in general and the role of CIN-like genes in leaf morphogenesis in Antirrhinum and Arabidopsis. Targets of CINCINNATA To understand how CIN controls Antirrhinum leaf shape, we first determined the consensus target site of CIN as GTGGTCCC by carrying out RBSS assay. Mutating each of this target sequence, we determined the core binding sequence as TGGNCC. Hence, all potential direct targets of CIN are expected to contain a TGGNCC sequence. Earlier studies suggested that CIN activates certain target genes that in turn repress cell proliferation. To identify these targets, we compared global transcripts of WT and cin leaves by differential display PCR and have identified 18 unique, differentially expressed transcripts. To screen the entire repertoire of differentially expressed transcripts, we have carried out extensive micro-array analysis using 44K Arabidopsis chips as well as 13K custom-made Antirrhinum chips. Combining the RBSS data with the results obtained from the micro-array experiments, we identified several targets of CIN. In short, CIN controls expression of the differentiation-specific genes from tip to base in a gradient manner. In cin, such gradient is delayed, thereby delaying differentiation. We also find that gibberellic acid, cytokinin and auxin play important role in controlling leaf growth. Genetic characterization of CIN-homologues in Arabidopsis Arabidopsis has 24 TCP genes. Our work and reports from other groups have shown that TCP2, 4 and 10 are likely to be involved in leaf morphogenesis. These genes are controlled by a micro RNA miR319. To study the role of TCP4, the likely orthologue of CIN, we generated both stable and inducible RNAi lines. Down-regulation of TCP4 transcript resulted in crinkly leaves, establishing the role of TCP4 in leaf shape. To study the function of TCP2, 4 & 10 in more detail, we isolated insertion mutants in these loci. The strongest allele of TCP4 showed embryonic lethal phenotype, indicating a role for TCP4 in embryo growth. All other mutants showed mild effect on leaf shape, suggesting their redundant role. Therefore, we generated and studied various combinations of double and triple mutants to learn the concerted role of these genes on leaf morphogenesis. To further study the role of TCP4 in leaf development, we generated inducible RNAi and miRNA-resistant TCP4 transgenic lines and carried out studies with transient down-regulation and up-regulation of TCP4 function. Upon induction, leaf size increased in RNAi transgenic plants whereas reduced drastically in miR319 resistant lines, suggesting that both temporal & spatial regulation of TCP4 is required for leaf development. Biochemical characterization of TCP domain To study the DNA-binding properties of TCP4, random binding site selection assay (RBSS) was carried out and it was found that TCP4 binds to a consensus sequence of GTGGTCCC. By patmatch search and RT-PCR analysis, we have shown that one among 74 putative targets, EEL (a gene involved in embryo development), was down regulated in the RNAi lines of TCP4. This suggests that EEL could be the direct target of TCP4. We have tested this possibility in planta by generating transgenic lines in which GUS reporter gene is driven by EEL upstream region with either wild type or mutated TCP4 binding site. GUS analysis of embryos shows that transgenic with mutated upstream region had significantly reduced reporter activity in comparison to wild type, suggesting that EEL is a direct target of TCP4. We have further shown that TCP4 also binds to the upstream region of LOX2, a gene involved in Jasmonic acid (JA) biosynthesis (in collaboration with D. Weigel, MPI, Tubingen, Germany). TCP domain has a stretch of basic residues followed by a predicted helix-loop-helix region (bHLH), although it has little sequence homology with canonical bHLH proteins. This suggests that TCP is a novel and uncharacterized bHLH domain. We have characterized DNA-binding specificities of TCP4 domain. We show that TCP domain binds to the major groove of DNA with binding specificity comparable to that of bHLH proteins. We also show that helical structure is induced in the basic region upon DNA binding. To determine the amino acid residues important for DNA binding, we have generated point mutants of TCP domain that bind to the DNA with varied strength. Our analysis shows that the basic region is important for DNA binding whereas the helix-loop-helix region is involved in dimerization. Based on these results, we have generated a molecular model for TCP domain bound to DNA (in Collaboration with Prof. N. Srinivasan, IISc, Bangalore). This model was validated by further site-directed mutagenesis of key residues and in vitro assay. Functional analysis of TCP4 in budding yeast To assess TCP4 function in regulation of eukaryotic cell division, we have introduced TCP4 in S. cerevisiae under the GAL inducible promoter. TCP4 induction in yeast cells always slowed down its growth, indicative of its detrimental effect on yeast cell division. Flow cytometry analysis of synchronized cells revealed that TCP4 arrests yeast cell division specifically at G1→S boundary. Moreover, induced cells showed distorted cell morphology resembling shmoo phenotype. Shmooing is a developmental process which usually happened when the haploid cells get exposed to the cells of opposite mating type and get arrested at late G1 phase due to the inhibition of cdc28-cln2 complex. This suggested that TCP4-induced yeast cells are arrested at late G1 phase probably by the inhibition of cdc28-cln2 complex. To further investigate how TCP4 induce G1→S arrest, we carried out microarray analysis and found expression of several cell cycle markers significantly altered in TCP4-induced yeast cells. Studies on crinkly1, a novel leaf mutant in Arabidopsis To identify new genes involved in leaf morphogenesis, we have identified crinkly1 (crk1), a mutant where leaf shape and size are altered. We observed that crk1 also makes more number of leaves compared to wild type. Phenotypic analysis showed that crk1 leaf size is ~5 times smaller than that of wild type. Scanning electron microscopy (SEM) showed that both cell size and number are reduced in the mutant leaf, which explains its smaller size. We have mapped CRK1 within 3 cM on IV chromosome.

Submitted by BELISA CRISTINA SAITO null (belisasaito@gmail.com) on 2017-04-20T18:20:53Z No. of bitstreams: 1 Tese Belisa Saito.pdf: 1868613 bytes, checksum: 40d639682537f01c2cc01e7a92791445 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-25T17:59:26Z (GMT) No. of bitstreams: 1 saito_bc_dr_ilha.pdf: 1868613 bytes, checksum: 40d639682537f01c2cc01e7a92791445 (MD5) / Made available in DSpace on 2017-04-25T17:59:26Z (GMT). No. of bitstreams: 1 saito_bc_dr_ilha.pdf: 1868613 bytes, checksum: 40d639682537f01c2cc01e7a92791445 (MD5) Previous issue date: 2017-03-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O milho é uma das culturas mais extensamente cultivadas em todo mundo. A incidência e a severidade de doenças têm aumentado significativamente nos últimos anos acarretando perdas no rendimento e afetando a qualidade dos grãos. Muitos trabalhos têm sido desenvolvidos na tentativa de identificar híbridos resistentes às principais doenças que acometem a cultura do milho, mas poucos são os relatos de estudos com linhagens. Dessa forma, o objetivo deste estudo foi: 1) identificar linhagens resistentes e susceptíveis com base na área abaixo da curva de progresso de doenças (AACPD) para os sintomas de ferrugem tropical (TR), ferrugem polissora (SR), cercosporiose (GLS), helmintosporiose (NLB), mancha marrom (PBS) e mancha branca (PLS); 2) identificar linhagens resistentes e suscetíveis com base nos parâmetros de adaptabilidade e estabilidade fenotípica para os sintomas de cercosporiose, helmintosporiose, mancha marrom e mancha branca; 3) identificar as melhores datas de semeadura, com a maior ocorrência das doenças, para fins de avaliação de linhagens e outros genótipos para resistência. Cinquenta linhagens, derivadas de populações com grãos flint e dent, foram avaliadas em blocos casualizados com três repetições, aos 45, 60, 75 e 90 dias após a semeadura em duas épocas, para medição da AACPD. Para a análise de adaptabilidade e estabilidade, 41 linhagens foram avaliadas em blocos casualizados com três repetições, 30 dias após o florescimento feminino, em onze épocas de semeadura, usando o método de análise de regressão. Foram atribuídas notas de 1, 2, 3, 4, 5, 6, 7, 8 e 9 correspondendo a 0, 1, 10, 20, 30, 40, 60, 80 e > 80% de área foliar com sintomas de doença. Para a AACPD, a análise de variância conjunta foi significativa para TR, SR, GLS e PLS e a interação linhagens x épocas foi significativa para ferrugem tropical e polissora. Para GLS e NLB as 41 linhagens foram classificadas como resistentes, sendo que as maiores severidades de doenças ocorreram nas semeaduras entre Junho e Setembro. As linhagens IVF1-3, IVF1-7, IVF1 -9, IVF1-10, IVF1 -11, IVF1 -25, IVF1-230, IVD1-2, IVD1 -2-1, IVD1-3, IVD1-9, IVD1 -12, 2F, 3F, 6F, 9F, 10F, 4C, 2D e 7D foram classificadas como resistentes para as doenças estudadas, sendo indicadas para o desenvolvimento de sintéticos. Para a mancha marrom e mancha branca, as semeaduras de Abril, Junho, Julho e Agosto apresentaram maiores severidades de doenças. As linhagens IVD1-9, IVD1-10, 7D, 10D e 2F podem ser indicadas no desenvolvimento de sintéticos resistentes. / Corn is one of the most widely cultivated crops in the worldwide. The incidence and severity of diseases affecting crops have increased significantly in the past years, leading to yield losses and affecting grain quality. Many studies have been carried out with the attempt to identify hybrids that are resistant to the main diseases, but few reports have studied inbred lines. Therefore, the objectives of this study were: 1) identify resistant and susceptible inbred lines based on the area under disease progress curve (AUDPC) for tropical rust, southern rust, gray leaf spot, northern leaf blight, physoderma brown spot and phaeosphaeria leaf spot; 2) identify resistant and susceptible inbred lines based on adaptability and stability parameters for symptoms of gray leaf spot (GLS), northern leaf blight (NLB), physoderma brown spot (PBS) and phaeosphaeria leaf spot (PLS); 3) identify the best planting dates, with the highest occurrence of diseases, for the purpose of evaluating inbred lines and other genotypes for resistance. For AUDPC, fifty inbred lines, derived from populations with flint and dent grains, were evaluated in randomized block designs with three replications, at 45, 60, 75 and 90 days after planting in two seasons. For the analysis of adaptability and stability, forty-one inbred lines were evaluated in randomized blocks with three replications, 30 days after silking, in eleven planting dates, using regression analysis method. The scale of scores from 1, 2, 3, 4, 5, 6, 7, 8 and 9 corresponding to 0, 1, 10, 20, 30, 40, 60, 80 and > 80% of leaf area with disease symptoms was used. For AUDPC, the joint analysis of variance was significant for TR, SR, GLS and PLS, while the interaction inbred lines x environments, was significant for TR and SR. For GLS and NLB, forty-one inbred lines were classified as resistant and the highest severities of diseases occurred in planting dates between June and September. The inbred lines IVF1-3, IVF1-7, IVF1 -9, IVF1-10, IVF1 -11, IVF1 -25, IVF1-230, IVD1-2, IVD1 -2-1, IVD1-3, IVD1-9, IVD1 -12, 2F, 3F, 6F, 9F, 10F, 4C, 2D and 7D were classified as resistant to the diseases studied and are indicated to produce synthetics. For PBS and PLS, the plating dates of April, June, July and August showed higher disease severity. The inbred lines IVD1-9, IVD1-10, 7D,10D and 2F may be indicated to produce synthetics.

No description available.

Call number: LD2668 .T4 1964 R71 / Master of Science

Call number: LD2668 .T4 1955 H39 / Master of Science