Thesis (MSc)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 54-60). Also available on the World Wide Web.

When light intensities become supersaturating for photosynthesis, phytoplankton must be able to protect the photosynthetic machinery from potential damage by excess energy absorption. One of the most important photoprotective mechanisms involves the nonradiative dissipation of excess light energy by the interconversion of the carotenoid pigments of the so-called xanthophyll cycle. Very little is known about how the xanthophyll cycle of natural communities of phytoplankton responds to high light conditions and the relationship of this photoprotective mechanism to the surrounding physical environment. The purpose of this thesis was to examine the functioning, activation and relationship to the physical environment of the xanthophyll cycle in phytoplankton from the Antarctic ecosystem and the Southern Ocean. Experiments in Antarctica were conducted in austral spring under various natural and artificial light regimes including the use of a newly developed light mixing simulator (LMS). Photoprotective carotenoid pigment concentrations were determined using a carotenoid specific protocol for High Performance Liquid Chromatography (HPLC). The photoprotective xanthophyll cycle was not active in Antarctic sea ice algae under the low light conditions under the annual sea ice. When sea ice algae are exposed to high irradiance, there was an initial rapid deepoxidation of the xanthophyll pigment diadinoxanthin (DD) to diatoxanthin (DT). With on-going irradiance exposure, slower deepoxidation of DD continued. The recovery of DD in the dark or under low light was found to be significantly faster than in temperate algal communities, and is likely a particular adaptation to the unique light environment in Antarctica. The temporal accumulation of pigments of the violaxanthin (VX) xanthophyll cycle was observed for the first time in a natural phytoplankton population. It is hypothesized that the VX cycle may function as a pathway to maintain the pool of DD cycle pigments rather than as a separate photoprotective pathway as observed in higher plants. The high irradiances of ultraviolet - B (290 - 320 nm) radiation (UVB) as a result of stratospheric ozone depletion over Antarctica in spring was found to significantly impact on the DD cycle. Exposure to high levels of both ultraviolet-A (320- 400 nm) radiation (UVA) and UVB reduced the photoprotective xanthophyll pigment pool with the greatest reduction occurring after exposure to high levels of UVB. The reduction in the amount of cellular DD after exposure to high levels of UVB was greater than can be explained by deepoxidation activity, which implies that high UVB exposure can lead to a loss of DD from the community. The first-order kinetic rates of the DD cycle were found to be similar to other studies and did not vary with light intensity. Simulations under natural light using the LMS demonstrated that the response of the DD cycle to static in situ incubations and when subject to vertical mixing was not similar, and that static incubations overestimate DD-cycle activity Over the long term, algae in a simulated vertically mixed environment were able to increase the pool of xanthophyll pigments compared to static conditions where the pool remained the same or decreased. Oceanographic observations from the subantarctic waters south-east of New Zealand in austral autumn provided the physical background for new insights into the xanthophyll cycle of Southern Ocean phytoplankton. The circulation flow and water masses between the Bounty Plateau and Bollons Seamount was resolved and shown to differ from numerical models. Relatively little of the warm and salty Subantarctic Mode Water (SAMW) from the Tasman Sea is carried in the flow of the Subantarctic Front (SAF). The spatial distribution of photoprotective xanthophyll pigments showed higher than expected concentrations in the surface mixed layer of the region. The high concentration of photoprotective pigments is considered to be a consequence of the low iron concentrations in southern waters and the highly variable light and vertical mixing environment. The high cellular concentrations of photoprotective pigments constrains photosynthetic activity implying that the photoprotective pigments may play a more significant role in controlling phytoplankton production in the Southern Ocean than previously thought. Analysis of the xanthophyll pigments and physical oceanography with a Self-Organising map (SOM) Artificial Neural Network (ANN) showed that the photophysiological index DT/ (DD+DT) can be used to resolve a change in water type properties. A simple numerical model was developed which can be used to provide a quantitative index of the relative magnitudes of vertical mixing and phytoplankton photoprotection in the water column. This approach may be useful to identify the effects of physical changes in the surface mixed layer of the Southern Ocean as predicted by climate change modelling.

Retinal detachment (RD) is a leading cause of blindness and although final surgical reattachment rate has greatly improved, visual outcome in many macula-off detachments is disappointing, mainly because of photoreceptor cell death. We previously showed that both lutein and Lycium barbarum polysaccharides (LBP) are neuroprotective in a rodent model of ischemia/reperfusion injury. The objective of this study is to investigate lutein and LBP as possible pharmacological adjuncts to surgery. Lutein: Subretinal injections of 1.4% sodium hyaluronate were used to induce RD in Sprague-Dawley rats until their retinae were approximately 70% detached. Daily injections of corn oil (control group) or 0.5mg/kg lutein in corn oil (treatment group) were given intraperitoneally starting 4 hours after RD induction. Animals were euthanized 3 days and 30 days after RD and their retinae were analyzed for photoreceptor apoptosis and cell survival at the outer nuclear layer (ONL) using TUNEL staining and cell counting on retinal sections. Glial fibrillary acidic protein (GFAP) and rhodopsin (RHO) expression were evaluated with immunohistochemistry. Western blotting was done with antibodies against cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9 to delineate lutein’s mechanism of action in the apoptotic cascade. To seek a possible therapeutic time window, the same set of experiment was repeated with treatment commencing 36 hours after RD. When lutein was given 4 hours after RD, there was significantly fewer TUNELpositive cells in ONL 3 days after RD when compared with the vehicle group. Cell counting showed that there were significantly more nuclei in ONL in lutein-treated retinae by day 30. Treatment groups also showed significantly reduced GFAP immunoreactivity and preserved RHO expression. At day 3 after RD, Western blotting showed reduced expression of cleaved caspase-3 and cleaved caspase-8 in the treatment group. No difference was found for cleaved caspase-9. When lutein was given 36 hours after RD similar results were observed. Our results suggest that lutein is a potent neuroprotective agent that can salvage photoreceptors in rats with RD, with a therapeutic window of at least 36 hours. The use of lutein in patients with RD may serve as an adjunct to surgery to improve visual outcomes. LBP: The same RD model was used for the LBP experiment. Phosphate buffered solution (PBS) or LBP in PBS was given orally through a gavage at 1mg/kg and 10mg/kg concentrations. For this experiment, animals were sacrificed 7 days after RD, and only cell counting of the ONL and TUNEL staining were performed. Both sets of results did not produce statistically significant changes with the use of LBP. Our preliminary data for the effect of LBP on retinal detachment shows no significant beneficial effect. / published_or_final_version / Medicine / Master / Master of Research in Medicine

Orientador: Elisa Helena Giglio Ponsano / Banca: Cecilio Viega Soares Filho / Banca: Otto Mack Junqueira / Resumo: A coloração da gema é dependente da absorção e da deposição dos carotenoides presentes na dieta da ave e representa uma característica sensorial de grande influência sobre a aceitabilidade do produto. O milho, ingrediente energético bastante utilizado na composição de ração de galinhas poedeiras, também apresenta potencial pigmentante, que deve ser explorado quando o objetivo é fornecer pigmentação à gema. Este trabalho teve como objetivo determinar as proporções entre pigmentos amarelos e vermelhos em rações contendo milho como principal fator energético para galinhas poedeiras visando promover a maximização da coloração de gema. Sessenta galinhas poedeiras da linhagem Dekalbe em fase de postura foram alocadas individualmente em gaiolas em galpão apropriado, onde receberam as rações experimentais durante 21 dias, com arraçoamento diário de 110 g e água à vontade. Foram aplicados 15 tratamentos, definidos por um delineamento composto central rotacional em que as variáveis estudadas foram os pigmentos amarelos provenientes dos ingredientes da ração (milho + farelo de gluten de milho), os pigmentos amarelos suplementares (luteína + zeaxantina) e os pigmentos vermelhos suplementares (cantaxantina), cada uma com três concentrações distintas. As aves foram pesadas no início e ao final do experimento e o peso dos ovos foi registrado diariamente. A cor das gemas foi determinada pelos métodos objetivo (L, a, b) e subjetivo (leque colorimétrico). A aceitação global das gemas foi determinada por meio de escala hedônica de cinco pontos. Os resultados obtidos foram submetidos a análises de variâncias, testes de comparação de médias (teste t e teste de Dunn) e à análise de regressão pela metodologia de superfície de resposta, adotando-se o nível de significância de 5%. O peso final das aves e o peso dos ovos não foram influenciados pelos diferentes... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The color of the egg yolk depends on the absorption and the deposition of carotenoids present in the hens' diets and represents a sensory characteristic of great impact on the product acceptance. Corn is commonly used as energy value ingredient for hens' diets formulations. Moreover, due to its additional pigmentation properties, it might be used to color egg yolk. The purpose of this research was to optimize the proportions between yellow and red pigments in hens' corn based rations to provide color maximization for yolks. Sixty Dekalbe laying hens were separately distributed in cages inside a rearing barn to receive the experimental diets for 21 days at a daily feeding of 110 g and water ad libitum. Fifteen treatments were defined by means of a central composite rotatable design in which the variables were the yellow pigments from the diets (corn + gluten meal), the yellow supplementary pigments (lutein + zeaxanthin) and the red supplementary pigments (cantaxanthin), each of them at three different concentrations. Hens' weights were recorded at the beginning and at the end of the experiment and the eggs weights were recorded daily. Yolks colors were determined by means of objective (L, a, b) and subjective (color fan) measurements. Global acceptance of yolks color was investigated with a five points hedonic scale. The results were analyzed by ANOVA, means comparison tests (t test and Dunn test) and regression analysis by Response Surface Methodology, at 5% significance level. Hens' final weights and eggs weights were not influenced by the treatments. Seven distinct colors for yolks were identified with the color fan. The most preferred yolks scored 9 and derived from the treatment which provided the highest yellow pigments concentrations (2.0 mg/hen/day) and no red pigments while the most rejected yolks scored 14 and derived from treatments which provided the highest concentration of red pigment (0.7 mg/hen/day), besides the yellow... / Mestre

Made available in DSpace on 2014-06-11T19:27:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-11-01Bitstream added on 2014-06-13T18:55:50Z : No. of bitstreams: 1 000739560.pdf: 1243049 bytes, checksum: 78c28184f41fbbc27555d54f96400d9d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The color of the egg yolk depends on the absorption and the deposition of carotenoids present in the hens´ diets and represents a sensory characteristic of great impact on the product acceptance. Corn is commonly used as energy value ingredient for hens´ diets formulations. Moreover, due to its additional pigmentation properties, it might be used to color egg yolk. The purpose of this research was to optimize the proportions between yellow and red pigments in hens´ corn based rations to provide color maximization for yolks. Sixty Dekalbe laying hens were separately distributed in cages inside a rearing barn to receive the experimental diets for 21 days at a daily feeding of 110 g and water ad libitum. Fifteen treatments were defined by means of a central composite rotatable design in which the variables were the yellow pigments from the diets (corn + gluten meal), the yellow supplementary pigments (lutein + zeaxanthin) and the red supplementary pigments (cantaxanthin), each of them at three different concentrations. Hens´ weights were recorded at the beginning and at the end of the experiment and the eggs weights were recorded daily. Yolks colors were determined by means of objective (L, a, b) and subjective (color fan) measurements. Global acceptance of yolks color was investigated with a five points hedonic scale. The results were analyzed by ANOVA, means comparison tests (t test and Dunn test) and regression analysis by Response Surface Methodology, at 5% significance level. Hens` final weights and eggs weights were not influenced by the treatments. Seven distinct colors for yolks were identified with the color fan. The most preferred yolks scored 9 and derived from the treatment which provided the highest yellow pigments concentrations (2.0 mg/hen/day) and no red pigments while the most rejected yolks scored 14 and derived from treatments which provided the highest concentration of red pigment (0.7 mg/hen/day), besides the yellow...

Marine brown algae (seaweeds) are a rich source of fucoxanthin, a xanthophyll carotenoid that is naturally, an accessory pigment in the process of photosynthesis of sea vegetation such as Sargassum incisifolium. Fucoxanthin has been exploited by nutraceutical companies for its anti-obesity effects that has resulted in an increase of seaweed slimming preparations such as FucoThin™. The field is getting widespread consumer attention as interest in fucoxanthin has also transcended to its widespread biological potential which include cytotoxicity, anti-diabetic, anti-oxidant, anti-inflammatory and anti-plasmodium effects. We therefore wanted to identify a reliable source(s) of fucoxanthin from diverse samples of South African marine brown algae in order to explore our medicinal chemistry interests around the cytotoxicity and anti-malarial potential of fucoxanthin. A known source, Sargassum incisifolium, was used to isolate (maceration in CH₂Cl₂/MeOH at 35 °C followed by a hexane/EtOAc step gradient silica column of the crude extract and reversed phase semi-prep HPLC) and characterize (1D and 2D NMR) fucoxanthin (reference standard) in order to develop an analytical method for its determination in selected diverse brown algae commonly found in South Africa. The HPLC [Column: Phenomenex® Synergi™ (250 x 3.0 mm i.d); Mobile phase: ACN/H2O (95:5)] method developed for this analysis was validated according the guidelines set by the International Conference on Harmonization (ICH). Fifteen species were then assessed for fucoxanthin content (μg/g of dried weight) using the developed method. Stability studies on fucoxanthin were also carried out to assess photo- and pH degradation of fucoxanthin. Zonaria subarticulata (KOS130226-18) from Kenton-On-Sea beach and Sargassum incisifolium (PA130427-1) from Port Alfred beach were found to be the highest producers of fucoxanthin with 0.50 mg/g and 0.45 mg/g dried weight respectively. Fucoxanthin was found to be both photo-labile and sensitive to both acidic and basic pH environments. However, the pigment was more photostable in pure as opposed to extract form and also showed to be more stable at pH 10.0. Our findings show that Z. subarticulata and S. incisifolium could be reliable sources of fucoxanthin and can be considered as the algae to use in optimized extraction procedures in further studies. Also, when working with fucoxanthin, it is important to protect it from light. Any consideration of taking fucoxanthin preparation orally (as a nutraceutical) should consider protecting the active from the harsh conditions of the gastrointestinal tract. Any upscale production of fucoxanthin from seaweed should consider variations such as geographical, seasonal, lifecycle stage, etc. of identified algae as these may be important factors in obtaining effective concentrations of fucoxanthin.

No description available.

Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2006. / Plants have evolved photosynthetic systems to efficiently harvest sunlight energy for the production of carbohydrates, but these systems also are extremely susceptible to an excess of light. To combat the potential damaging effects of light, plants have developed various mechanisms to control and cope with light stress. These mechanisms include the movement of either leaves, cells (negative phototaxis) or chloroplasts to adjust the light-capturing potential, the adjustment of the light-harvesting antenna size through gene expression or protein degradation, the removal of excess excitation energy either through an alternative electron transport pathway or as heat. However, the latter mechanism based on thermal dissipation, remains the most effective to rid the plant of damaging excess light energy. This process involves several carotenoid pathway pigments, specifically the de-epoxidised xanthophyll cycle pigments. The process and extent of thermal dissipation in plants can be measured and quantified as non-photochemical quenching (NPQ) of chlorophyll fluorescence by using well-established methodologies. Several Arabidopsis and Chlamydomonas mutants affected in the xanthophyll cycle have been isolated. These mutants have provided evidence for the correlation between the de-epoxidised xanthophyll cycle pigments and NPQ as well as better understanding of the operation of the xanthophyll cycle and the related carotenoid biosynthetic enzymes. This key photoprotective role of the xanthophyll cycle is therefore a promising target for genetic engineering to enhance environmental stress tolerance in plants. Several genes from the carotenoid biosynthetic pathway of grapevine (Vitis vinifera L.) were isolated previously in our laboratory. The main aim of this study was to over-express two xanthophyll cycle genes from grapevine in Arabidopsis and to analyse the transgenic population with regards to pigment content and levels as well as certain photosynthetic parameters. The transgenic lines were compared with wild type Arabidopsis (untransformed) plants and two xanthophyll cycle mutants under non-limiting conditions as well as a stress condition, specifically a high light treatment to induce possible photodamage and photoinhibition. Transgenic Arabidopsis lines over-expressing the two V. vinifera xanthophyll cycle genes, β-carotene hydroxylase (VvBCH) and zeaxanthin epoxidase (VvZEP), were established following Agrobacterium transformation. In addition to the untransformed wild type, two NPQ mutants, npq1 (lacking violaxanthin de-epoxidase) and npq2 (lacking zeaxanthin epoxidase), were used as controls throughout this study. The transgenic lines were propagated to a homozygous T3-generation, where stable integration and expression of the transgenes were confirmed in only 16% and 12% for VvBCH and VvZEP lines, respectively. No phenotypical differences could be observed for the transgenic lines compared to the wild type, but the npq2 mutant showed a stunted and ‘wilty’ phenotype, as was previously described. To evaluate the pigment composition of the transgenic lines a reliable and reproducible method was needed to analyse carotenoids from leafy material. To this end a new high-performance liquid chromatography (HPLC) method was developed for the quantitative profiling of eight major carotenoids and chlorophyll a and b. Emphasis was placed on baseline separation of the xanthophyll pigments, lutein and zeaxanthin as well as the cis- and trans-forms of violaxanthin and neoxanthin. The method effectively distinguished Arabidopsis wild type plantlets from the two NPQ mutant lines (npq1 and 2) and could possibly find application for green leafy tissue samples in general. The carotenoid content of the NPQ mutants were in accordance with previous reports. The lack of zeaxanthin epoxidase activity in the npq2 mutant resulted in the accumulation of zeaxanthin under both low and high light conditions. This high level zeaxanthin was found to cause an initial rapid induction of NPQ at low to moderate light intensities, but this difference disappeared at high light, where zeaxanthin formation induced considerable NPQ in the wild type. Similarly, the npq1 mutant was unable to de-epoxidise violaxanthin to zeaxanthin under high light conditions, which resulted in severe inhibition of NPQ induction. Furthermore, these mutant plantlets were shown to be more susceptible to photoinhibition compared to that of the wild type. The over-expression of VvBCH resulted in a marked increase in the xanthophyll cycle pool pigments (violaxanthin, antheraxanthin and zeaxanthin) and reduced β-carotene levels under both low and high light conditions compared to that the wild type, indicating elevated β-carotene hydroxylase activity possibly due to over-expression of the VvBCH gene. Similar to the induction of NPQ in the npq2 mutant, the increased levels of zeaxanthin in the VvBCH lines did not offer any additional photoprotection. This would suggest that the heightened zeaxanthin levels observed for the VvBCH lines do not necessarily enhance photoprotection, however may protect the thylakoid membrane against lipid peroxidation as has been shown previously. The VvZEP lines however, showed reduce levels of zeaxanthin in high light conditions to that of the wild type, probably due to the competing epoxidation and de-epoxidation reactions of the xanthophyll cycle. This reduction in zeaxanthin synthesis in the VvZEP lines resulted in significant reduced NPQ induction compared that of the wild type, a phenomenon also observed for the npq1 mutant. Similar to the npq1 mutant, these lines displayed significantly increased photoinhibition, which may be due to photodamage of the reaction centers if one considers the lowered photosystem II photochemistry efficiency and reaction center openness of these lines compared to the wild type. This may suggest that even small reductions in zeaxanthin amounts can result in an increase in photoinhibition, under high light conditions. This study and its results provide fundamental information regarding two grapevine-derived carotenoid pathway genes and their possible physiological roles. Moreover, studies like these provide information that is essential when possible biotechnological approaches are planned with this central plant metabolic pathway in mind. The results highlighted the complex regulation of this pathway, necessitating attention to flux control, simultaneous manipulation of several pathway genes, and the measurement of other compounds derived from this pathway when evaluating the possible applications of the carotenoid pathway of plants.